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Ramesh Gangatharan
University of Technology Sydney
All content following this page was uploaded by Ramesh Gangatharan on 24 November 2014.
Statement of Originality
Ramesh GANGATHARAN.
Comparison between Piled Embankment and Load Transfer Platform - Rigid
Inclusion for Soft Soil.
Ramesh Gangatharan - Completed on spring 2014.
In the process of designing structures over soft soils, geotechnical engineers face many
challenging problems. These can range from enormous lateral pressures and
movements, bearing failure, unbearable settlement, and local or global instability. The
piled embankment and the inclusion of geosynthetic layers have proved to be
economic and efficient alternatives. They are applied in places such as airport runways,
road and rail embankments, bridge abutment approach roads, storage tanks, subgrade
improvements and segmental retaining walls. The piled embankment can be used on
soft soils; particularly when surface and differential deformation is restricted and
limited time is available for construction. The principal property attributed to the
geosynthetic success is its ability to cover the needs of load transfer, reduce the
yielding of soil, which is on top of the pile head, the total reduction of differential
settlements and the restricting the lateral movement.
The main goal of this project is to compare two different types of piled embankment.
These are piled embankment with inclined piles at the batter slope of the embankment
(old way – popular in 1960"s to 1980"s) and piled embankment with geosynthetic
reinforcement (modern method) also known as the Load Transfer Platform (LTP)
based on its mechanism, design, construction and costs. Furthermore, a numerical
study was conducted using PLAXIS 2D on the two different types of pile
embankments. The analysis was carried out by observing the settlement, lateral
displacement of the embankments and pile, vertical stress on the ground surface, forces
and bending in piles. The given recommendations come as a result of completed tests
and literature review from relevant sources.
The research provides a great contribution to the engineering industry as it deals with
a broad topic of design and the construction of piled embankment all in one report. On
the top of this, the most useful design techniques used in the traditional piled
embankment technique is re-visited.
Table of Contents
Statement of Originality .................................................................................................. 1
Acknowledgements......................................................................................................... 3
List of Figures
Figure 1: Column Supported Embankment (CSE) / Pilled Embankment (Collin, 2004) ......... 11
Figure 2: Column supported embankment with Geosynthetic Reinforcement - Load Transfer
Platform (SCDOT, 2010) ......................................................................................................... 11
Figure 3: Piled Embankment used for road extension (Suzanne, 2008) ................................ 15
Figure 4: Placement of Geogrid (Suzanne, 2008) .................................................................. 16
Figure 5: Embankment fill (Grubber, 2007) ........................................................................... 18
Figure 6: Timber Columns (google, 2014) .............................................................................. 24
Figure 7: Piles- supported embankment (a) on end bearing piles (b) on floating piles (Collins,
2007). ..................................................................................................................................... 26
Figure 8: Non head-settling piles vs head-settling pile (a) with firm end bearing stratum (b)
without firm end bearing stratum (floating pile)- (Collins, 2007).......................................... 27
Figure 9: Placement of Geosynthetic reinforcement............................................................. 28
Figure 10 Equipment access to the site (suzzane, 2007) ....................................................... 29
Figure 11: Piled embankment for Netherland airport runway project.................................. 30
Figure 12: Reinforced fill materials (NHWI, 2006) ................................................................. 31
Figure 13: Geosynthetic reinforcement (NHWI, 2006) .......................................................... 32
Figure 14: Ultimate Limit States for reinforced piled embankments .................................... 38
Figure 15: Serviceability State ................................................................................................ 39
Figure 16: Column Layout ...................................................................................................... 41
Figure 17: Plan view diagram showing the tributary area for a triangular pile grid .............. 42
Figure 18: sequence of Soil Arching (McKelvey III, 1994) ...................................................... 48
Figure 19: Catenery Theory.................................................................................................... 49
Figure 20: Beam Theory ......................................................................................................... 49
Figure 21: Description of soil Arching analysis with Terzaghi's method ................................ 51
Figure 22: Soil wedge model: (a) 2D and (b) 3D .................................................................... 53
Figure 23: Spanning a square grid of square supports - (a) ................................................... 56
Figure 24: Soil arching (a) Experimental evidence (b) Equilibrium analysis at crown of arch
(c) Equilibrium analysis at just above pile cap ....................................................................... 57
Figure 25: Typical vertical stress distribution of embankment fill along the centre of pile
spacing with Multi-Arching model ......................................................................................... 59
Figure 26: Swedish Method Load Distribution between Coumns ......................................... 61
Figure 27: A section view of the 2D problem illustration the various quantities involved in
the design calculations........................................................................................................... 65
Figure 28: A plan view of the pyramid used for the LTP design calculations. Dotted lines
represent where the geogrid layers intersect the pyramid. .................................................. 66
Figure 29: Influence of embankment height to stress concentration ratio (Han and Gabr,
2002) ...................................................................................................................................... 69
Figure 30: The change of efficacy to the ratio of spacing to embankment height (Sovulj,
2005)....................................................................................................................................... 69
Figure 31: The influence of pile stifness on the stress concentration ratio, geosynthetic
tension and differential settlements (Gangaakhedar, 2004) ................................................. 71
Figure 32: The influence of embankment fill friction angle on the efficacy (Jenck et al, 2007)
................................................................................................................................................ 73
Figure 33: The comparison between 2-D plane strain and 3-D analyses (Kempton et al,
1998)....................................................................................................................................... 75
Figure 34: Distribution of pore water pressure in clay at the centre of piled embankment (a)
immediately after construction (b) after 2 years) .................................................................. 76
Figure 35: Site Location and Layout (NHI, 2006) .................................................................... 79
Figure 36: T-Wall Block Diagram (NHI, 2006) ......................................................................... 83
Figure 37: Typical Cross-Section (NHI, 2006) ......................................................................... 86
Figure 38: Vibro-Concrete Column Load Test Results ............................................................ 89
Figure 39: Map showing project site in relation to St.Michael and the twin Cities. .............. 91
Figure 40: Plan view of site prior to highway expansion........................................................ 92
Figure 41: The cross-section ................................................................................................... 93
Figure 42: A plan view of the instrumented region of LTP..................................................... 94
Figure 43: Diagram showing components of vibrating wire concrete embedment strain
gage. ....................................................................................................................................... 95
Figure 44: Plan view and perspective view of concrete embedment gage installation......... 96
Figure 45: embedment strain gage ........................................................................................ 96
Figure 46: Foil gage with waterproofing on pile wall ............................................................. 97
Figure 47: Spot-weldable vibrating wire strain gage installation on pile wall. ...................... 98
Figure 48: Basic components of an earth pressure cell. ........................................................ 99
Figure 49: Constrution of Wat Nakorn – In bridge Approaches, Bangkok (Tencate, 2013) . 105
Figure 50: Typical long section through the basal reinforced piled bridge approaches
(Tencate, 2013)..................................................................................................................... 106
Figure 51: Construction of pile caps and connecting beams (Tencate, 2013) ..................... 106
Figure 52: Embankment steep reinforced fill slope(Tencate, 2013) .................................... 107
Figure 54: Piling the embankment foundation (Tencate, 2013) .......................................... 108
Figure 55: Constrution of A1/N1 dual carriageway, Ireland (Tencate, 2013) ...................... 109
Figure 56: Laying Geolon® PET geotextile reinforcement (Tencate, 2013).......................... 109
Figure 57: Driving concrete piles through the working platform (Tencate, 2013) .............. 110
Figure 58: driving concrete piles through the working platform (Tencate, 2013) ............... 111
Figure 59: Typical cross section through the Geotextile reinforced piled embankment
(Tencate, 2013)..................................................................................................................... 112
Figure 60: Completed piled embankment (Tencate, 2013) ................................................. 112
Figure 61: Constrution of M74 Motorway Completion, Glasgow, UK (Tencate, 2013) ....... 113
Figure 62: geotextile reinforcement around anchor block at edge of piled area (Tencate,
2013)..................................................................................................................................... 113
Figure 63: Typical cross section through the approach embankment (Tencate, 2013)....... 114
Figure 64: One of the approach embankments under construction (Tencate, 2013) ......... 115
Figure 65: embankments nearing completion (Tencate, 2013) ........................................... 115
Figure 66: Embankment geometry with the soil profile (Ariyarathne, 2014) ...................... 119
Figure 67: Lateral Displacement ........................................................................................... 124
Figure 68: Lateral Displacement at the toe of the embankment ......................................... 125
Figure 69: Vertical stress on the ground surface at the base of the embankment ............. 126
Figure 70: Settlement profile along the ground surface...................................................... 128
Figure 71: Settlement profile at the embankment crest. .................................................... 129
Figure 72: Maximum Shear Force in Pile ............................................................................. 130
Figure 73: Maximum Bending in Pile ................................................................................... 131
Figure 74: Maximum Lateral Displacement in Pile .............................................................. 131
Figure 75: Lateral Displacement – Shades ........................................................................... 132
Figure 76: Vertical stress distribution inside the embankment........................................... 133
List of table
Chapter 1 - Introduction
The construction of highway embankments over soft, compressible soil resulted in
many issues including huge settlements, embankment consistency and prolonged
timeframes for consolidating the foundation of the soil. As a result, there were
developments and wide usage of the different ground improvement methods.
Specialists have used wick drains, stone columns, surcharge loading, geo-synthetic
reinforcement, deep soil combination and vibro-concrete columns to deal with the
problems of settlement and embankment stability pertinent to the construction,
involved. The engineers have, on the other hand, adopted advanced technique: column
support embankments (CSE) which are in recent years strengthened with geo-synthetic
reinforcement, in situations where limitations on time are crucial for the project's
success. The use of this technology has achieved success in various projects in
Australia and the world over the past 2 decades.
1.1 Description
The next type of CSE is a geo-synthetically reinforced load transfer platform (LTP)
which may be employed to reduce the number of piles needed to provide support to
the embankment and improve the design efficiency. There are one or more layers of
the geo-synthetic reinforcement in the LTP that are situated among the uppermost of
the piles and lowermost of the embankment. A CSE that has the geo-synthetic
reinforcement is shown in Figure 2. This type of CSE are currently most used rigid
solution method around the world.
Figure 2: Column supported embankment with Geosynthetic Reinforcement - Load Transfer Platform
The focus and scope of this report is on the 2 types of Column Supported
Embankments described in the previous page. The drive of this report on the CSEs is
to recognize the subjects that have been resolved successfully through CSE and
develop the existing state-of-the-practice of CSE design, configuration and elaborating
on their construction, usage and shortcomings. A clear comparison of these 2 types of
CSEs are shown and their designs have been evaluated using PLAXIS models and
Excel. Furthermore, the focus and scope of this report pertains to providing guidelines
for the CSE selection procedure. In places where more extensive technical background
can be provided, references have been cited, while the general costs are stated so that
a preliminary technical and economic assessment can be carried out with respect to
ascertaining the ability of CSE to solve a particular issue.
Scandinavia was the first country in which pile-supported embankments were widely
implemented during the 1960's period. Details and various deductions about pile-
embankments have been made by Rathmayer (1975) in his paper in which details on
three different embankments built in Finland, which have been tested using earth
pressure cells and load cells, have been discussed and conclusions have been drawn
accordingly. These instruments have been used in order to find out the process of the
transference of the embankment loads on to the piles, the way in which vertical
pressure is disseminated uniformly over the pile cap and finally the effects that can be
observed if the shape of pile caps changes with the change in the loading
embankments. The conclusions that were made from these tests helped to identify the
shape of the pile cap which is more efficient and feasible for use. Conclusions include
the fact that nearly 30-50% of the area at the base of the embankment has been all
covered by piles, also known as pile cap coverage. It was found out that the distribution
of stress over the pile was immensely scattered with greater concentration being on the
outer ring of the area of the cap. About 75% of the load from the branch of river had
to be carried by the pile. From these facts it was inferred that circular pile caps are
much more effectual in comparison to rectangular shaped pile caps as circular pile caps
can bear 10% greater loading for the equivalent expanse and under similar conditions.
However, the paper does not mention any detail about the geosythetic reinforcement
being used on the pile caps.
Detailed study regarding the use of pile embankments for bridges has been carried out
by Reid and Buchanan (1984). The study was carried out in Scotland. By making use
of a sheath cover just above the pile caps helped to reduce the area beneath the pile
cap to get populated and this also helped to promote arching. The use of reinforcement
also proved beneficial as it helped to reduce the size of the pile cap being used and
thus the formation of the bends at the top of the piles no longer remained much of
concern with respect to the design of pile caps. Reinforcements helped to use the pile
cap of any shape. The earth pressure cells were placed just above the pile cap and the
results that were obtained were harmonized with the results obtained by Rathmayer
that is the pressure was concentrated at the outer area of the pile cap. The other two
findings that is the pile coverage area and tributary load taken up by the pile were
found different from that obtained by Rathmayer. The pile coverage area was
calculated as 11% and the loading on the pile was found to be 82%.
Another study includes that of Fluet et al. (1986) in which the effect of geogrid layer
on the base of the embankment was tested. The embankment that has been used for
this purpose had been extended on two supports. Inflatable air bags having the property
to distribute pressure evenly and provide easy control over pressure distribution have
been used as the material in between the two supports. The actual scenario is definitely
different but the issue associated in the actual system of piles supporting the
embankment is somewhat identical to that faced using inflatable air bags. Therefore,
this model could be easily used to study the actual scenario and make conclusions. The
conclusions that have been obtained from the interaction between geogrid and arching
action associated with the column supported embankment system have been studied
and explained in detail in numerous literature works. In all these studies a unanimous
conclusion was seen that the use of geogrid layer at the base of the embankment
encouraged the process of arching whereas if geogrid layer was omitted from the
embankment system no significant arching could be observed.
A special design of embankment which had been used to provide support to a toll plaza
in South Wales, UK have been discussed in detail regarding the scheme, efficiency
and efficacy of the system in the paper presented by Maddison et al. (1996). The
embankment had been built using vibro concrete columns and the arrangement was
made in a rectangular grid pattern. The columns were used to provide support for a
platform designed using layers of biaxial geogrid. This platform had been used to
transfer loads. This platform was covered on top using a layer of rock filled
embankment. The various tests on this embankment in order to find out the
sustainability and pressure handling ability of the columns and embankment were
carried out by using number of hydraulic pressure cells and settlement makers. Tests
were carried out for several months after the construction of this toll plaza and
embankment and it was observed that there wasn't any sort of mobility of the
embankment even after one whole year. The settlement among the columns was found
to be 40- 50mm. As the construction
levels increased, the pressure at the
platform just above the columns
increased but remained within the
maximum value which had been
predicted using the various analyses
carried out. However, the pressure at
the base of columns was found to be
small which ultimately resulted in
arching. Figure 3: Piled Embankment used for road extension (Suzanne,
case measurements for the erect pressure just above the columns and in between them
were analysed and results were obtained. Also the sideways displacement and
pressures were observed using vertical inclinometers and then these values were
compared and investigated with the calibrated values acquired from Finite Layer
Analysis of Consolidation (FLAC) technique.
Vega- Meyer and Shao (2005) have discussed and analysed a rather analogous
embankment design to the one mentioned above. These embankments which were
located in Colon City of the republic of Panama were horizontally braced using MSE
walls and vertically reinforced by columns. This embankment and column system also
had a load transfer platform atop of it. This platform had four layers of uniaxial geogrid
placed in crosswise and longitudinal alignment alternately with reference to the test
embankment. The test process carried out on other embankments were also carried out
on this and it was determined that the vertical pressure measured in between the piles
at the platform's base was 18% of that found over the pile caps.
The pressure value on the geogrids was found to be 1%. The maximum and differential
settlement at the base of designed
embankment was calculated using 2D
analysis. However, the value of
settlement calculated atop the load
transform platform (LTP) 132 days
after the construct ion was negligibly
small. The displacement values
between the piles found out at the top
and bottom of the load transform
platform (LTP) were similar. The Figure 4: Placement of Geogrid (Suzanne, 2008)
displacement between the piles was
calculated using sensors placed in between the piles. The readings for the
displacement and settlement were taken 132 days after the construction was over
because the sensors had malfunctioned.
Plometux et al. (2004) carried out a detailed study on an embankment situated east of
London, England. The embankment was supported using 2193 controlled modulus
columns and this embankment was tested using a series of numerical analysis. Values
for settlements, pressure in the geotextile layers and between piles, soil stability, etc.
were calculated in order to determine the stability and efficiency of the embankments.
In this part, the uses, advantages and disadvantages, as well as the design specifications
of the CSE technology are going to be elaborated.
2.2.1 Application
The CSE technology essentially tries to shift the loads of embankment through the
columns and towards a competent soil or rock layer below the soft foundation soil.
CSE's traditional role has been to offer support to embankments across soft soil when
there is not sufficient time for consolidating the soft foundation soil when wick drains
and surcharge loads are being utilized, or when there are issues connected to
differential or total settlement and complete stability. The CSE usage is most suitable
for the following purposes in the transportation field:
Embankment stabilization
Roadway expansion / widening
Bridge approach fill stabilization
Bridge abutment and other foundation support
The technology is also used for other purposes, which include foundation support for
storage tanks and commercial office buildings (i.e. shallow foundations that require
CSE support), and maintaining wall foundation support. A number of successful
projects continually increase as newer, more cost effective systems are being
produced. It means that there will be further development of the CSE technology in
future. The CSEs serve as a practical substitute when it is not possible to develop
traditional embankments because of issues pertaining to time, stability or environment.
It is used to stabilize extensive area loads like highway embankments. There is the
medium to high fills on soft soils in these applications, as well as embankment fills
that may be restricted by the retaining walls of the Mechanically Stabilized Earth
In the future, substantial amounts of highway expansion and reconstruction work are
going to be required. In a few of these works, it would be required to construct more
lanes right next to the existing highways developed on medium to high fills on soft
cohesive soils like those present in wetland regions. It is essential to consider
differential settlement between current and new construction, as well as the stability
of the embankment in such scenarios. Supporting the new fill on the CSE also provides
a feasible design that can be an alternative to the traditional construction. Other uses
of the CSE include supporting bridge approach fills, offering stability and decreasing
the expensive maintenance from settlem ent at the intersection between approach fill
and bridge. A column supported embankment for the approach embankment was used
by the New Jersey Light Rail for a river crossing in 2001(FHWA, 2006). On one side
of the embankment, there was a modular concrete retaining wall system, while the
other portion consisted of the embankment in a slope that went downwards towards
the adjoining grade. In the CSE, Vibro-Concrete Columns (VCC) were used as
columns and there were three layers of the geo-synthetic reinforcement to develop the
LTP (Young et al., 2003) such that the "bump" at the edge of the bridge could be
The placement of embankment fills is not time consuming as there is very little or no
load put by the embankment on soft foundation soil. When the conditions are
favourable, CSE can be created to larger heights as compared to traditional means of
embankment across soft foundation soils. Hence, it is likely to expand the approach
fills by decreasing the length of the bridges. Bridge abutments can receive support of
the CSE at areas that do not have the capacity to support abutments on traditional
shallow foundations. In these areas, mechanically stabilized earth walls supported on
the CSE are also used. The use of the CSE for supporting building foundations in those
regions where foundation soils are soft and compressible has been quite successful.
The CSE is used as a technical and possibly economical substitute to a more standard
means of construction (i.e. staged construction with or without the geo-synthetic
reinforcement, surcharge loading and wicks drains). With the CSE, the pore water
pressure dissipates in the soft foundation soil immediately resulting in no waiting
periods. Hence, construction takes place more quickly in one stage, which is the most
important advantage of this technique. In addition, it is more feasible in economic
terms to use CSE as compared to the approach of removing and replacing deep poor
bearing soils, especially for the huge sites in which groundwater is near the surface.
CSE may lead to a substantial decrease in total and differential settlement of the
embankment. In addition, in areas that do not allow high-vibration approaches to be
used, columns for the CSE system may be chosen such that they reduce or remove the
possibility for vibrations.
The CSE technology holds another paramount advantage, which is that it is not
restricted to usage of certain columns. Rather, the designer has the option of choosing
the most suitable column for the project. When very soft soil at the site is expected,
the column type chosen for the project may be the VCC, GEC, timber piles or augured
piles. On the other hand, for contaminated soils, the kind of columns selected may be
such that they do not create any spoils during the installation. In areas that have
stronger foundation soils, it may be more appealing in the economic sense to use stone
columns or rammed aggregate piers.
188.8.131.52 Disadvantages
The initial construction cost is usually the only crucial disadvantage posed by the CSE
as compared to other options. However, the cost may turn out to be much lower as
compared to other alternatives when time savings brought about by the CSE
technology are considered in the economic assessment.
There should be limited initial spacing of the columns to have 10-20% of the
area replacement ratio (i.e. the ratio of cross-sectional portion of the pile to the
How the installation affects the environment should also be considered when
deliberating on the most suitable column system. For instance, when the project was
considering the use of stone columns, vibro-replacement stone columns were usually
jetted in position that led to the elimination of finer parts of the affected soil. The
ensuing fines-laden jetted water needs to be contained for a short period so that the
sediment deposition and disposal can take place.
In addition, the unidentified pollutants may be eliminated and moved to the
atmosphere by the jetting water. The designer may opt for another column system that
does not substitute the in-situ soils (like dry vibro-displacement stone columns, VCC,
GEC etc.). There are different laws in different countries for the way these operations
should be carried out. In addition, columns for the urban areas, where it is not
appropriate to have noise and vibrations are chosen to keep in view these aspects.
There are different alternatives for ground improvement systems that should be
factored in when assessing with two types CSE methods highlighted in this report.
These include staged construction with or without the geo-synthetic reinforcement,
surcharge loading with or without wick drains and lightweight fill. Further information
on these alternates (Lightweight Fill, Wick Drains, and MSE Walls and Reinforced
Slopes) can be obtained from Geotechnical journals and Reports. Their design and
construction methods are not part of the scope of this report. However when it comes
to time constraint construction projects these alternate methods are not suitable when
comparing with CSEs. Apart from the various alternatives to ground enhancement
systems, designers also need to take into account the possibility of employing bridge
structure when building embankments on soft, compressible soils.
A extensive variety of Columns can be used for CSE. For the pile supported
embankments, conventional piles can be used (for instance, timber, steel pipe, steel H,
pre-cast concrete and cast-in-place concrete shell). On the other hand, the structural
capability of conventional piles, apart from timber piles, is quite high (i.e. 400-2000
kN). It is normally not a requirement for the CSE and so they are not as appealing in
the economic sense as compared to the present day columns. In European industries,
augured piles have been successfully utilized. In recent years new types of columns
have been developed which includes Stone Columns, Geopier Rammed Aggregate
Piers, Deep Soil mixing Columns, Geotextile Encased Columns (GEC) and Vibro-
Concrete Columns (VCC).
The CSV supports are developed by including dry granulated material in the lenient
foundation soil through an auger with a compaction head linked to its tip. The new
technology was only recently introduced in the United States from Germany. The usual
diameters of the CSV columns are 150-200 mm and their capacity is 45-90 kN. The
auger undergoes rotation in opposite directions to the flights' pitch. Hence, soil is not
eliminated during the drilling function; instead, it is enclosed around the auger. When
the auger moves into the ground, it encloses the soil in the auger's surrounding. While
the auger is being removed, dry granulated material (usually a mixture of sand cement)
is moved to the auger's tip and compacted.
AU-Geo piling system is a new system that includes a PVC pipe installed over a
mandrel through the soft foundation soil and inside the solid bearing layer. The new
system which was created in Holland includes an enlarged plate which is fastened
towards the lower portion of the PVC pipe to improve the column's end-bearing
resistance. A steel pipe with a diameter of 220-mm is installed into the ground as deep
as the bearing requires. The mandrel includes a 15 mm PVC pipe and end plate that is
smaller in size in comparison to the internal diameter of the mandrel. The mandrel is
then eliminated to position the PVC pipe that is full of concrete. The dimensions of
pile cap usually fastened to the pile are 300 mm by 300 while the greatest capacity of
the AU-Geo pile is 150 kN.
As mentioned in previous page there are several options available to the designers with
respect to the columns that serve as an important element of the CSE. It is usually
considered that driven piles are extremely stiff columns that have a modulus of
elasticity ranging from 7,000 to 210,000 MPa
(modulus of timber piles is 7,000 MPa).
Minipiles and augured piles are
characteristically drilled pipes and are also
believed to have stiff columns. The foundation
soil's capacity usually governs the settlement
of these kinds of columns.
The modulus for stone columns and rammed aggregate piers such as Geopiers is quite
lower as compared to driven piles as it ranges between 30-60 MPa. The VCC are a
similar technology to stone columns, however, they are a lot stiffer than stone columns
as concrete substitutes the stone in this column. In more recent times, GEC, AU-Geo
and CSV columns that have been developed. These systems are also not as stiff as
driven piles, like rammed aggregate piles and stone columns.
The columns that CSE might use are listed in the Table shown below, plus their key
Range of
Typical Column
Column Type Allowable
Lengths (m) Diameters
Capacity (kN)
Timber pile 100 – 500 5 – 20 300 – 550
Steel H pile 400 – 2000 5 – 30 150 – 300
Steel pipe pile 800 – 2500 10 – 40 200 – 1200
Pre – cast Concrete
400 – 1000 10 – 15 250 – 600
Cast-in-place concrete
400 – 1400 3 – 40 200 – 450
shell (mandrel driven)
Shell driven without
500 – 1350 5 – 25 300 – 450
Augured piles 350 – 700 5 – 25 300 -600
Micropiles 300 -1000 20 – 30 150 – 250
Deep mix method
400- 1200 10 – 30 600 -3000
Stone columns 100 – 500 3 – 10 450 – 1200
Goopier rammed
225 – 659 3 – 10 600 -900
aggregate piers
CSV (combined soil
30 – 60 3 – 10 120 - 180
AU – Geo 75 – 150 2- 15 150
Large deformations are likely to occur, as soft soils cannot tolerate external loads
exerted by the embankment and the traffic. The loads are moved to the greatly firmer
columns in the piled embankments. Prefabricated columns are generally used in this
case, or in the other case cast in place displacement piles are used. Generally, timber
or concrete columns with a diameter from 100 to 300 mm are used. But 600 mm
diameter piles must been used. The piles are driven in the ground till a competent
stratum is reached. Often, the piles cannot reach the competent stratum, when the soft
clay layer is thick. These piles are then termed as the floating piles. In south East Asian
region, Bakau timber piles of maximum 4.5 to 6 m length are used. Pile caps are used
to upsurge the load transmission to the piles. The area covering ratio is used to
determine the size of the pile.
Figure 7: Piles- supported embankment (a) on end bearing piles (b) on floating piles (Collins, 2007).
The piles are entrenched into the ground till a competent stratum of firm soil or hard
rock is reached, in order to support the embankment. This is shown in the above figure.
Often the piles are unable to reach a firm soil, when the soft clay layer is thick. In this
case, the piles are termed as floating piles.
The factor related to the head settling and non-head settling is not an important factor
of consideration relative to the design embankment and geosynthetic tensile strength.
The settlement of the pile base to an extent and the shortening of some of the piles will
assist in the settling of the head settling piles. As shown in the figure below, smaller
differential settlement of the geosynthetic layer is caused. According to the rigidity of
the columns and the asset of the bearing layer, end bearing columns. In the same
manner, the pile penetration depth and the pile stiffness will also turn the floating piles
into head settling and non-head-settling columns. In practical application however, the
end bearing piles are found not to settle and usually act as non-head settling piles while
floating piles can act as both settling and non-head settling piles. This paper will
review the different terminologies related to embankment on end bearing and floating
piles, as these terms are conveniently used to differentiate the studies.
Figure 8: Non head-settling piles vs head-settling pile (a) with firm end bearing stratum (b) without
firm end bearing stratum (floating pile)- (Collins, 2007)
There are two kinds of load transfer platforms (LTPs) that shift the load of
embankment to the columns. A strengthened concrete structural mat may be employed
for this purpose. An LTP of this kind needs to have a structural design of the mat to
make sure that the load effectively shifts to the columns. In general, concrete mats are
not feasible in economic terms and so they are not going to be elaborated upon in this
The other LTP includes one or more deposits of the geo-synthetic support and certain
backfill to generate a structure which allows for shifting the embankment load to the
footing piles. The design and configuration of the LTP along with the geo-synthetic
reinforcement are going to be the focus of the rest of this paper.
Geosynthetic Reinforcement
oad transfer platforms are generally built using geo-synthetic reinforcement material
with either one layer of high strength geotextile or geo-grid, or multiple layers of
biaxial geo-grid that has lower strength. The design model that is employed for
assessing the LTP (the catenary or beam), the distance between the columns, and the
embankment height determine the kind of geo-synthetic reinforcement used and its
strength. For several designers,
it is important to have a
cushion layer of fill between
the upper portions of the
columns and the geo-synthetic
reinforcement to remove
abrasion that takes place
between the upper portion of
the column and the
reinforcement. The direction
given in the construction
Figure 9: Placement of Geosynthetic reinforcement
drawings should be followed
when rolling out the geo-synthetic reinforcement. It is important to remove all wrinkles
and slack before fill placement. While fill placement is occurring, construction
equipment should be pre vented from directly moving on the reinforcement. At least
150 mm of fill should be added between the reinforcement and any construction
The structure and choice of geo-synthetic reinforcement should take into account the
seam requirements. Both sewn seams and overlap seams have been employed in the
LTPs built so far; however, the design of the LTP should consider the kind of seam to
be used.
Backfill Material
A very vital element of the system is the backfill material, utilized for the construction
of the LTP. Shifting the load from the embankment to the piles essentially requires
arching in the soil over the columns. Hence, the soils in the area where the arch is
developed should be of frictional material that has high shear strength. It is believed
that well-graded granular fill is the most appropriate material that should be used for
building the platform. Over the platform, a non-select fill may be utilized to develop
the rest of the embankment.
3.3 Equipment
Select Reinforced Fill – reinforced fill materials have to fulfil the gradation
specifications given below. The liquid limit of the reinforced fill material going
through No. 40 sieve is required to be lower than 40 along with a plasticity index of
lower than 20. Reinforced fill materials are going to be grouped according to the
unified soil classification system as GW or GW-GM.
Size % Passing
200 mm 100
38 mm 95-100
4.75 mm 65-40
0.425 mm 40-20
0.075 mm 0-15
Figure 12: Reinforced fill materials (NHWI, 2006)
Technical Specifications
The placement of select reinforced fill should be in horizontal layers, such that
it does not go beyond 250 mm in non-compacted thickness for heavy
compaction equipment. In those areas where compaction is attained using
hand-operated compaction equipment, the placement of fill should be in
horizontal layers, such that it does not go beyond 150 mm in non-compacted
The compaction of select reinforced fill would take place to at least 95%
maximum dry density as has been established according to ASTM D-1557
The plan region of the platform should determine the measurement for payment
of the LTP.
The payment made to the contractor will be on the basis of unit price per square
meter of plan region for supplying and fixing the load transfer platform. This
consists of the select fill and geo-synthetic reinforcement.
The structure and installation of the columns are part of the performance requirements,
in addition to the load transfer platforms. It is not possible to discuss specifications of
all the column types in this report. The Design and Construction of Driven column
Foundations and Micropile Design and Construction Guidelines should be reviewed
for obtaining information of performance conditions of the piles before selecting it.
The section's purpose is to provide information regarding design and configuration of
load transfer platform alone. The modes of failure that need to be evaluated with
respect to the design and construction submitted by the Contractor are clearly
explained in this specification. However, the Contractor should have the authority to
select the design approaches. When the specifying agency requires a certain design
method to be used for building the load transfer platform, then that approach should
be employed.
At least two weeks before the work commences, the Contractor should provide shop
drawings to the Engineer for evaluation. These should suggest the load transfer
platform thickness, the spacing and configuration of the columns, the number of
reinforcement layers to be used and the upright distance between deposits of
reinforcement. In addition, it should suggest the desired capacity of the reinforcement
Scope of Work
The details of the technical and quality assurance requirements for dealing with
management, labour, equipment, material and other important services that are
essential for the design and build of the LTP are provided in this performance
The references that support this documentation should be made available to the
Engineer at least 30 days before the construction commences. The Contractor in charge
of the design and construction of the load transfer platform should have an experience
of at least 3 years in the field of installing geo-synthetic reinforcement.
Site Preparation
It is the contractor's responsibility to make preparations for the subgrade and eliminate
any deleterious materials. The Geotechnical Engineer employed on the site should
examine and authorize the foundation soil before the select reinforced fill is situated.
Geo-synthetic Reinforcement
A certificate should be presented by the Contractor which affirms that the design
specifications are fulfilled by the reinforcement. These pertain to the eventual strength,
creep, installation damage, durability and coefficient of interaction for sliding as per
the design approval gained.
The approved drawings should be adhered to when building the column supported
Acceptance Criteria
A test section that has at least four rows of columns in either direction is going to be
built. The plans approved by the Contractor should be adhered to when installing the
test embankment. After the installation of the geo-synthetic reinforcement, the
embankment will be built. To observe settlement of the subgrade and settlement at the
embankment's surface, settlement plates are going to be installed. Depending on the
design a surcharge load of ___ kN/m2 is going to be put on the test embankment and
the settlements noted. The settlements are going to be approved when the measured
surface settlement of the columns when the surcharge load is applied is lower than __
Quality Assurance
Estimating the cost of the piled embankment is relatively straight forward. The
components of the piled embankment are the select reinforced fill, pile materials,
geosynthetic reinforcement and the labour to install these materials. Select fill cost
range from as low as $20 – 50/ ton depending on location and availability. The
geosynthetic reinforcement coast can vary from $20 -30/ m2 . The thickness of of load
transfer platform / soil arching may be estimated for preliminary cost purposes to be
one-half the clear spacing between columns ((s-d)/2). The labour to construct the
embankment maybe estimated to be 50% of the total cost of the materials to construct
the pile supported embankment system.
A preliminary cost estimate for a column spacing 3m, with a column diameter of 0.5
meter and a unit cost of $20/m2 for the geosynthetic reinforcement and $30/ ton ($6.75
/ kN) for select fill is given below.
Because of the multiple types of columns that are available, it is not practically feasible
to provide cost guidelines for all the column types. At this stage the initial cost for
conventional column supported embankment are cheaper than CSE with Geosynthetic
Reinforcement (LTP) assuming that the pile diameter in both method are same. The
maintenance cost/ life cycle cost for conventional column supported embankment are
higher than CSE with Geosynthetic Reinforcement (LTP). Overall cost is depend on
the embankment height and other design parameters.
The piled embankment designs contain the layout of the embankment, piles and the
geo-synthetic. The piled embankment can be designed in a number of different ways.
The present guidelines for creating designs of the piled embankment contains some of
the ways in which they can be designing of the embankments can be done. The German
method (EBGEO), the British Standard 8006 and the Nordic Guidelines, and are some
of the ways of designing piled embankments.
The aspects of limit state, and serviceability state failure criteria need to be considered
in the construction of column supported embankments. Figure below demonstrates the
limit state failure modes. In, the piles should be structured such that they hold the
upright load of the embankment lacking deteriorating. Normally, it is presumed that
the columns hold the entire load of the embankment. The horizontal amount of the
piles below the embankment should be ascertained. The design of LTP must be such
that they vertical load is shifted from the embankment to the columns. It needs to be
determined whether there is the possibility of lateral sliding of the embankment on the
upper portion of the piles. Lastly, assessments regarding overall steadiness of the
system should be carried out.
Apart from the limit state assessment, serviceability state enterprise also needs to be
discussed. The stress in the geosynthetic strengthening that is utilized for the
development of LTP needs to be maintained lower than the highest threshold so that
inappropriate deformation reflection at the upper portion of the embankment can be
avoided (i.e. differential settlement). An analysis of the settlement of the columns also
needs to be carried out so that it can be assured that there is no inappropriate settlement
of the entire system.
The typical design steps for a pile supported embankment are presented as below:
i. Determine an approximate value of the initial column spacing (refer to the
guidelines of feasibility analysis).
ii. Find out the column load needed.
iii. Choose the initial column type on the basis of the column load needed and
site's geotechnical considerations.
iv. Find out the capacity of the pile to fulfil the requirements of limit and
serviceability state design.
v. Find out the degree of piles that are needed over the width of the
vi. Choose technique for designing LTP (i.e. beam or catenary).
vii. Find out the requirements for reinforcement on the basis of column spacing
calculated earlier in the first step. Revise the column distance if needed.
viii. Establish requirements for reinforcement for lateral spreading.
ix. Ascertain the complete reinforcement requirements on the basis of LTP and
lateral spreading.
x. Determine global stability.
xi. Generate construction drawings and measurements.
The choice of pile types are mainly made on the basis of load capacity, constructability
and costs. It is normally presumed that the embankment and any surcharge load are
completely held by the column. The load that should be borne by a column is generally
established on the tributary region for each pile.
To demine the design upright load in the pile, tributary region of the soil around each
column is required. Even though a regular hexagon is formed by the tributary region
around the pile, it can be carefully estimated as being a circle having equal total area.
The pile loads which have a center-to-center pile spacing of 1.5 m need to fall in the
range of around 110-250 kN for embankments that have a height of 3-10 m. The load
required for a centre-to-centre column spacing of 3 m is almost 400-1100 kN when
embankment has a height in the range of 3-10 m. Once the required load in the column
has been found, Table given in A.4.3.1 can be used to choose the column type that is
going to give the desired capacity at minimal costs.
The pile loads that strain measurement are used to determine might be compared the
tributary load Wtr, the material weight in the pile's tributary area Atr. The geometric
area that belongs to every pile in a standardized pile grid is known as the tributary area.
If the area of a grid is triangular in shape, the tributary area is always hexagonal in
shape. The equation used to calculate the weight is given by the equation given below.
Figure 17: Plan view diagram showing the tributary area for a triangular pile grid
The further severe stability analysis utilizing limit equilibrium methods can be
evaluated using the British approach. It is adequate to use the basic British method for
initial designs and/or feasibility studies.
The possibility of horizontal dispersal of the embankment is very critical. The design
of geosynthetic reinforcement must be such that it precludes horizontal dispersal in the
embankment. This is an important feature of the design; as several piles that are fitting
for piled reinforced embankments do not have the capacity to offer sufficient lateral
resistance to avoid embankment spreading without failing.
The design of the geosynthetic reinforcement must be such that they oppose the
horizontal pressure because of the embankment's lateral spreading. The tensile
pressure needed to avoid lateral spreading (Tls) can be obtained using the equation
given below:
𝑇𝑙𝑠 = 𝐾 (𝛾𝐻 + 𝑞)𝐻
2 𝑎
𝑐𝑖𝑒𝑚𝑏 = coefficient of interface for slipping between the geosynthetic support and
embankment fill.
The design of the embankment's geometry, its stability and the process for the transfer
of the load through the soil arching, are all part of the embankment's design. The
geometry is selected in a way that meets the criteria set out for the construction, the
stability of the embankment, and the formation of the soil arching. The common slope
stability analyses are used to assess the steadiness of the embankment. These analyses
include the Bishop's method and the Fellenius's method. The arithmetical analysis
method consisting of the finite element method can also be used.
The relative clarity and definitiveness of the embankment's geometry design and its
stability leaves the mechanism for the load transfer as the only area where uncertainties
of the embankment design may exist. This mechanism is provided by the arching of
the soil and it should be the focus of the efforts made to better the piled embankments
design methods. The stress travels through the embankment with the help of the soil
arching. The external load and the embankment loads are transferred to the columns
through the arching of the soil. This process can be better understood if it is analysed
analytically and also by taking the guidelines into consideration.
McNulty (1965) describes arching as the capability of any material to transmit loads
between two points when there is a relative displacement between them. The loads are
sent by a mechanism involving shear stresses. The soil arching does not take place
when the soil mass is located over a firm base as difference drive is not possible
(McKelver III, 1994). A number of empirical techniques have been introduced to
develop a model for the soil arching. The next section contains more detail on soil
A. Soil Arching
Soil arching significantly affects the load transfer processes of the Column supported
embankments since they require the embankments to be of a certain height enabling
arching within them. This in turn brings down the settlement of the surface, and goes
on to provide a smooth surface for the same. However, the presence of the arches
above the columns increases the stress on the corresponding DC over time which is
attested to by actual physical observations, centrifuge model tests and numerical
modelling (Ali and Huat 1993, Fang 2006, van Eekelen et al. 2011, Huat et al. 1994,
Inagaki et al. 2002 and Chen et al. 2008). Since the DCM piles are stiffer in comparison
to the softer soil surrounding them, this inadvertently sees significant portions of the
traffic loads on the embankments being moved to the piles and ultimately providing
for difference settlements between the piles and the softer soil surrounding it. Shear
stress is correspondingly seen in the embankment fill, which in turn distributes the load
on the vertical embankment from the soil to the harder columns by soil arches formed
between two piles (Terzaghi 1943, Kempfert et al. 2004). The membrane action in the
geosynthetic layer allows for fractions of the weight in the soil wedge below the arch
to be moved to the columns by the geosynthetic layer tension. This reflects the load
transfer process to be a system of arching in the embankment fill between the DCM
columns and is dependent on the membrane action in the geosynthetic layer.
The arching concept forms the basis for the majority of current design procedures in
circulation for embankments supported by DCM columns, but they have the drawback
of the theories all differing on descriptions of the arch shape and processes on its
development. Quite a few of the texts allow for full arching once the embankment has
been constructed to a certain extent, and the parameters of the arch development are
concluded. Low et al. (1994), Abusharar et al. (2009) and Hewlett and Randolph
(1988) are of the common perception that the arches are positioned in a semicircular
format, without overlapping, within a two-dimensional plane with the column width
being double to the arches. However, these theories are yet to discuss the development
of the arch design. BS8006 (2010) has also accounted for semi-circular arcs in its texts,
but has simultaneously also accommodated for partial and complete arching concepts
dependent on the embankment height and the distances between the piles.
Accordingly, it is theorized that complete and partial arching happens in instances of
H > 1.4 (s - a) and 0.7(s - a) ≤ H ≤ 1.4 (s - a) respectively, in which H represents the
embankment height's the pile spacing s is the calculated pile diameter. Considering
that H alters alongside the placement of individual layers, there is always the option of
a partial arch being changed to a full arch while the embankment is under construction.
Collin et al. (2007) has described the American process for CSE design which allows
for triangular arches being taken against 2D plane strain situations, and with the edges
being angled at 45° degrees. Guido et al. (1987) also considered similar designs where
arches in a triangular formation are placed with 45° internal angles. The horizontal
plane in this scenario is a 2D plane strain, and has a corresponding pyramid for a 3D
The Swedish design and methodology has been forwarded by Rogbeck et al. (1998)
who is of the recommendation to use triangular shaped arches, but incorporating 30 °
angles at the tip of the slice in the soil under two-dimension plane strain situations.
However, this model has not accounted for the process of arching development from
the embankment construction perspective. Kempfert et al. (2004) has proposed the
German EBGEO2004 for GRCS embankment constructions where the standard
vertical pressure working upon the DCM column and the softer foundation soil
adjacent to it are calculated taking into perspective the hemispherical shaped domes
lying across pile caps. This is perhaps very similar to what has been proposed by
Hewlett and Randolph (1988). The major difference in the German theory against the
Swedish is the presence of multi-shell domes in the arches. The outermost shell is
similar to a hemisphere when the embankment height is more than half of the spaces
between the columns. However, when the same height parameter is below half the
column spacing, the arch height is at par to that of the embankment, although at the
direction of the column head level, the shell dome radius increases and makes the
curvature smaller. Kempfert et al. (2004) have not debated upon the change from
fractional to full arcing, although aspects of filling materials and the lenient foundation
soil are considered during the application of arching concepts to calculate the
embankment load in the fill.
The soil arching phenomenon is shown in Figures below. In Figure (a), the load at
point "a" is equivalent to the overburden stress γH, where y refers to the soil's unit
weight and H is the soil mass height. A temporary true arch is created the point at
which soil loses support. At point "a", the soil is undergoing tension, and the soil
prism's weight begins shifting to the unyielding soil closest to it (Figure b). This leads
to deformation of the momentary true soil arch. When the soil reconciles into an
inverted arch (Figure c), a state of equilibrium is attained, the nearby unyielding soil
activates its shear strength and the whole load is transferred. The shifting of stress has
fully taken place at a certain height (He) above point "a". Above this point, the
settlements in soil mass are consistent.
The soil arch ratio (р) refers to the extent of soil arching, and is the ratio of mean
vertical load on yielding segment to the mean vertical load because of embankment
fill and surcharge load.
р=𝜎𝑠 /(γH+q)
Load transform platform can essentially be designed using two methods. In the first
method, reinforcement functions as a catenary and is the one that is employed by the
British Standard, the Swedish and the German approaches. Through the reinforcement,
the load is shifted from the embankment fill to the piles by passing through catenary
tension in the strengthening. The reinforcement essentially functions as a structural
component and any advantages obtained by the
development of compound strengthened soil mass
are disregarded. This can be seen in Figure.
The other methodology to develop the LTP, called the Collin Method, is occasionally
called the Guido Method. The Collin Method of reinforcement employs multiple
reinforcement layers to develop a stiff reinforced soil mass. The reinforced soil mass
functions as a beam that shifts the LTP over the platform to the piles beneath.
Apart from soil arching, the load transfer platform construction takes into account
tension membrane theory. The reinforcement holds the upright load from the soil
within the arch and any surcharge load when the embankment width is not sufficient
to create the complete arch. The tension in the strengthening can be calculated using
various theories (Fluet and Giroud). It is not possible to go into a lot of detail on the
tension membrane theory in this Technical Summary.
To facilitate the use of references, symbols used by the British Standard, German,
Swedish and the Collin Methods have been standardized. The symbols that are most
commonly going to be used when discussing these approaches have been presented in
Figure below.
The basis for this technique is a slice shaped soil arcing which was put forward by
Carlsson (1987). The cross-sectional area of the soil wedge underneath the soil arcing
is represented by a slice with an internal apex angle of 30 degrees (Figure).
The critical height is considered in this method and an extra load over the wedge is
transmitted to the columns in a direct way. A 2-D method involves the consideration
of the embankment's height above the triangle and the soil wedge's weight per unit
length is estimated as:
The estimated weightiness of the soil wedge is equivalent to the load on the geo-
synthetic layer. The remaining load of the embankment is supported by the columns.
Svano et Al (2000) has introduced a technique which includes the 3-D effect. This
technique is displayed in Figure 22. The weight of the soil mass per pile cap side,
which is transmitted to the geo-synthetic, can be estimated as:
ws - Weight of soil per pile cap side (half pyramid)
a - width of square pile caps
b - Centreline spacing of piles
r- unit weight of the embankment
H - height of embankment
Β - The slope depicted as shown in figure
This technique that reflects a pyramid type arcing is standard primarily in the
Scandinavian countries.
It has been suggested by the British Standards that the embankment height should be
at least 1.4x the clear distance between piles. This makes certain that difference
settlement does not take place at the embankment's surface. Soil arching that has
occurred between neighbouring columns brings about higher vertical pressure on the
piles as compared to the foundation soil around it. The equation presented below is
created on the basis of Marston's formula. It gives the ratio of vertical pressure on the
piles to the mean vertical pressure at the embankment base.
𝑃𝑐′ 𝐶𝑐 𝑑 2
= [ ]
𝜎𝑣 ′ 𝐻
Pc' = vertical stress on the coloumn
σv'(the average vertical stress at the base of the embankment) =(𝑓𝑓𝑠 γH+𝑓𝑞 )
𝐶𝐶 =anchoring coefficient*
d=column diameter
In cases when 0.7 (s-d) ≤ H ≤ 1.4 (s-d), the dispersed vertical load borne by the
reinforcement can be found using the equation given below:
The tension inherent in the extensible strengthening (Trp) for each lineal meter of
strengthening due to the dispersed load is given as follows:
Trp =0.5 WT [ s-d⁄d ](1+ 1⁄6ε )
The preliminary tensile stress in the strengthening is required for creating a tensile
load. To make sure that all embankment loads are shifted to the columns, a realistic
upper boundary of 6% strain should be enforced.
When the reinforcement deforms due to the embankment weight, tensile load (Trp) is
created. This usually takes place when the embankment is being built, however in
cases when reinforcement does not deform throughout construction, the strengthening
will not hold the loads till there is foundation settlement. The equation given above is
suitable for those supports that can go through deformation throughout loading (i.e.
extensible supports). For supports that are not extensible, different relationships should
be employed to find out their desired strength.
To make sure that long-term difference deformations do not take place on the
embankment's surface, the long-term stress on the reinforcement (because of creep)
needs to be kept as low as possible. A minimum creep strain of 2% should be permitted
above the design life of the reinforcement.
Hewlett and Randolph (1988) introduced this technique which is established on the
assumption that the embankment arcing is in the shape of a hemispherical dome shell
which can be seen in Figure b and c. The arching shell's thickness is b/2 in the diagonal
arrangement of the square off column grid and b is the width of the square off column.
The soil stresses are assumed to be redistributed in the arcing shell alone because of
the soil arching. The stress circulation outside the shell is the same as the stress
distribution in the beginning. This shows the stress increases linearly with depth above
and below the arching shell. It is assumed that the arching fails either at the crown of
the arch or the pile cap.
Two equations were developed by applying equilibrium analyses at the two locations.
These equations deal with the stress on the surface of the sub soil (σs) as shown below:
The examination is conducted in the plane strain of the arcing shell having sphere-
shaped geometry. Figure 24(b) shows the vertical equilibrium of the soil at the crest
of the arch.
Figure 24: Soil arching (a) Experimental evidence (b) Equilibrium analysis at crown of arch (c)
Equilibrium analysis at just above pile cap
The arch consists of four plane strain arcs at the pile cap. Each one of them takes up a
quadrant of the cap. Figure shows the equilibrium study in the plane strain at the
sections of the pile cap.
The larger value obtained between the results of Equations shows the larger stress
experienced on the surface of the subsoil. The Hewlett and Randolph formula produces
a vertical pressure circulation of the embankment body along the arching dome's
center. This can be seen in Figure above. This technique is better than the BS 8006
technique as it considers the embankment fill's strength and some help from the soft
soil counter pressure is also included.
Kempfert et al. put forward a multi shell arching concept which is used in the new
German method. The technique of Hewlett and Randolph (1988) is also considered in
this method and alterations are made for embankments of low height by employing the
multi shell arcing theory. Domed arches between columns or pile caps are considered
and the equation for this method is derived by considering the vertical equilibrium as
can be seen in Figure.
The vertical pressure circulation in the embankment body along the pile spacing's
center is displayed in Figure below. This model enhances the pressure redeployment
model in the embankment body and also includes the uphill lenient soil counter stress
which may exist between the columns (Alexiew, 2005).
Figure 25: Typical vertical stress distribution of embankment fill along the centre of pile spacing with
Multi-Arching model
There are several similarities between the Swedish method and the British Standard.
For the Swedish method to be valid, the assumptions/parameters given below need to
be satisfied:
Arch is created
Loading causes deformation of the reinforcement
A single reinforcement layer is used
Strengthening is situated within 0.1 m over the column
The height of embankment is more than or equivalent to the clear gap between
Ratio of pile or pile cap area to affect area per pile is higher than or equivalent
to 10%.
The effective friction angle of the embankment fill is 35%.
Initial stress in the support is restricted to 6%.
Long-standing (creep) strain is restricted to 2%.
Total strain is lower than 70% strain at failure.
The model that is employed in the Swedish method to find out the vertical load borne
by the reinforcement can be seen in Figure below. The soil wedge shown in the figure
allows for estimating the cross-sectional region of the soil below the arch, which is the
stress that the support bears. This is also applicable when the height of the embankment
is less than the upper part of the soil wedge (i.e. (s-d)/(2 tan 150)).
The equation given below provides the 2D weight (WT) of the soil wedge:
The load distribution allows for calculating the three-dimension impacts, when the
load gets dispersed on the surface can be seen in figure. The load is carried by the
reinforcement across the boundaries of the column. The equation given below allows
for determining the force in the support for each lineal meter of depth, because of the
vertical load in 3D:
Trp = 0.5 [ 1+(s⁄d) ] WT (1+ 1⁄6ε )
In order to evaluate the bearing capacity of the soil, Guido et al (1987) conducted
plate loading tests on geo-grid reinforced soil masses. As a better and more refined
method of this, the Collin method was used which has taken its essence from the
work of Guido. Experiments determine that some heaving is observed as
unreinforced sand exhibits a local shear failure mode in which the shear surface
extends. As displacement increased, the load after failure remained fairly constant.
On the contrary, sand that is reinforced seemingly followed a punch failure mode. In
the punch failure mode no surface heaving is visible and below the edge of the plate,
failure surface extends. This is apparent by an obvious deflection of the geo-grid at
the location. Moreover, it was found that the ideal number of layers for increasing
bearing capacity was three beyond which layering does not benefit capacity bearing.
Among the conclusions reached by the work of Guido et al. Bell et al. (1994)
emphasised on the fact that the angle of load spread above a pile can be estimated to
be 45 degrees as far as the angle of internal friction is at least the same value, in a
reinforced soil mass. To the reversed problem of a soil mass resting above a pile,
Jenner et al. (1998) used the work of Guido et al. And Bell et al. to apply on it. As
mentioned by Pierpoint and Russell (1997), the probable effects of gravity on the
issue are not accounted for. Several case histories are cited in which "enhanced
arching" design was made use of successfully including Topolnicki (1996) and
Maddison et al. (1996).
Jenner's ideas are followed by the Collin Method in the concept's approach. A Load
Transfer Platform (LTP) is formed as three layers (typically) are used made of
vertically spaced geo-grid, ad are positioned within well compacted select fill. The
basic purpose of the geo-grid is to provide horizontal closure to the fill, which makes
transfer of the embankment load to piles much more efficient. The secondary
purpose of the grid is to provision the loose soil below the arched region. Certain
assumptions are made in the design that are given below (Collin 2004):
Over a region made by an angle of 45 degrees from the pile cap edge, soil
arching occurs.
A pyramid-shaped region is formed between each group of three piles by the
loose soil supported by the geo-grid.
The whole embankment load over the LTP is shifted to the piles.
The LTP's thickness is either the same or greater than the clear span between
piles, or the shortest possible distance between the corners of the adjacent pile
A number of three layers of geo-grid are used minimum to form the LTP.
5% is the limited strain the geo-grid initially should have.
Mentioned below are the steps that explain the Collin method (Collin 2004), which
was used to design the embankment. Quantities that are used in the design are
provided in brackets.
Based on the former experience, estimates are made regarding the shape of the pile
grid, center to center pile spacing s and the pile cap diameter and cap shape. The pile
spacing is limited by the capacity and height of the embankment [equilateral
triangular grid with s = 2.13 m, d = 0.61 m.]
The whole embankment load is supposed to be lifted by the piles. Supposing that a
standard distribution of the embankment load exists on the pile grid, every pile is
used to support the tributary load Wtr. The triangular spacing is as follows
According to the load of the design, and spacing a suitable pile type is selected. If
pile load is excessive, the load and spacing can be adjusted accordingly.
The pile design and the platform design are considered differently. However, the
treatment is dependent on the grid spacing and spacing. Also, the shape and size of
pile caps has to be accorded to. The LTP's design's main component is working out
the tensile load in the geo-grid.
i. An assumption is made that the region within the LTP is above a boundary
defined by ≤ 45 degrees from horizontal at the edge of the pile cap. Figure
below shows a less complex 2D illustration of this. Another assumption then
made is that depending on the pile layout, soil forms a three sided or four
sided pyramid by the non-arching soil. A three-sided pyramid is shown in
plan view in the Figure as it is in the current project.
Based on the spacing of the pile, the height ha of the apex of the pyramid is described
in the last step is calculated as described below:
Where s is center – to – center spacing of piles and d is the pile cap diameter. The
LTP thickness h should be greater than or quual to ha [ha = 0.76 m, h = 0.91m]
Figure 27: A section view of the 2D problem illustration the various quantities involved in the design
ii. The geo-grid's layer has a particular spacing that is pre-defined. (Note:
Although this particular design does not abide by this rule, the Collin
considerations state that the minimum spacing should be 8 20 cm)
iii. The lower of the following two values determines the strength of the geo-
grid. a) The allowable creep limited strength at maximum strain (5%) and b)
given the safety factor, the allowable strength.
iv. The weight of the fill material between layer n and the n +1 layer, which is
directly over it, divided by the area of layer n, is used to calculate the
standard vertical stress; Wn.
v. Based on the 2D tension membrane theory, tensile load per unit length Tn is
calculated. This is for the geo-grid layer n.
Where Ω is a dimensionless factor determined from strain level[ ex: Ω = 0.97 for 5%
strain and Dn is design span as shown in the figure below, calculated for triangular
spacing as,
Figure 28: A plan view of the pyramid used for the LTP design calculations. Dotted lines represent
where the geogrid layers intersect the pyramid.
The methodical methods for calculating the transfer of the load (soil arcing effect) are
of limited usefulness. Jones et al. (1990) gave the causes for these limitations. First of
all, empirical equations are used to describe the arching process between the pile caps
placed next to each other. Another reason is that the techniques developed do not
correctly consider the partial foundation support under the geo-synthetic
The numerical analysis technique is more precise and it can be used to study the
complicated interactions in the structure of the soil and the piled embankments. The
factors affecting the working of the piled embankments can also be considered. These
factors are not included in the analytical techniques.
Several terms have been used by different authors to describe the transfer of load, the
geo-synthetic tension and the way the piled embankments settlements respond in the
numerical analysis techniques.
5.6.1 Definitions
Certain definitions have been employed by various researches to establish how well
the piled embankment is working. The terms defined below will be referred to in the
coming sections.
The efficiency 'E' of the column support is stated to be the fraction of the weight of
the embankment carried by the column caps. Hewlett and Randolph (1988) define it
Sovulj (2005) defines efficacy as the ratio of the load carried by the column, which
consists of skin friction and base resistance, to the load of a single cell embankment.
McNulty (1965) used the term "soil arching ratio" to express the level of soil arching.
To explain the same effect, Kempton et al. (1998) adopted the term "stress reduction
ratio" in their writing. This essentially means that both the terms have the same
meaning attached to them. This meaning associated with the terms is explained below.
Geo-synthetic Tension
Quantitative research shows that tension is not homogenous through the length of
geosynthetics, rather the most tension occurs at the pile edge. It is usual due to design
purposes that highest amount of tension is paid attention to most, and is of most
The complicated structure of soil can be analysed with the help of numerical analysis.
The analysis can incorporate approximately all parameters that affect the working
capability of a piled embankment. Several researchers have performed parametric
studies making use of quantitative data and analysis. In these studies the embankment
on end bearing piles and floating piles have been separated, and are not treated as the
same. This seems to be a more generalized approach, and a simpler one instead of
having taken into account the embankment on non-head-settling piles and on-head
settling piles. The former reflection is not discoursed in the review of literature apart
from the influence discussed of stiffness of pile.
The load transferred to the piles will increase with the increase in the embankment
height. The increase of the height of embankment will also increase the stress
concentration ratio. Han and Gabr (2002) have demonstrated this effect through 2-D
axisymmetric finite difference analyses and 2-D axisymmetric finite element analyses
of piles embankment correspondingly. The effect of the embankment height to the
stress concentration is shown in the figure below. The same study was also carried out
by Suleiman et al (2003) through 2D plane strain analyses.
The load transfer mechanism is estimated by some of the researchers through the
definition of soil arching ratio. There is a reduction in the soil arching ratio
asymptotically to a certain value with the resultant increase in the embankment height.
Similar results were obtained by Suleiman et al (2003) through the 2D plain strain
analyses, while a higher value was obtained through the 3-D analyses with the
conformation of the behaviour (Kempton et al., 1998).
The term efficacy is also used to express the load transfer. An increase in the efficacy
with the increase in the embankment height was visible in the results obtained by Van
der Stoel et al., (2006) and plane strain analyses by Jenck et al., (2007). A comparative
analysis between the numerical calculations of efficacy and the calculation results
from the empirical methods was also provided by Van der Stoel et al., (2006). Lower
efficacy was demonstrated by the empirical values as compared to the numerical
methods. Larger scatter was evident in the results of the various methods.
The term efficacy was used by Sovulj (2005) to express the load transfer, according to
the study conducted by Hewlett and Randolph (1988). The load carried by the piles
was however only considered in the study, when the piles were with caps. Efficacy
was aggregate up to a convinced extreme value with the upsurge in the embankment
height, relative to the low shear strength embankment fill material.
Figure 29: Influence of embankment height to stress concentration ratio (Han and Gabr, 2002)
Figure 30: The change of efficacy to the ratio of spacing to embankment height (Sovulj, 2005)
A reduction in the efficacy will be observed with the increase in the embankment
height, above this value. According to studies, there is an optimal charge of
embankment height for specific column spacing. In the presence of high shear strength
of the embankment fill material, the optimum value will not be found.
The escalation in the embankment height will lead to the increase in the extreme and
difference settlements of column supported embankments as well as geosynthetic
tension. This observation has been asserted by all the studies. A significant part was
also played by the construction of the embankment to the final height, as stated by the
study of Russell and Pierpoint (1997). When the embankment fill was positioned in
one step, higher extreme settlements, stress in pile head and geosynthetic tensions were
observed as compared to when embankment was filled stepwise.
Pile Spacing
The embankment loads transferred to the piles are reduced by increasing the pile
spacing. The efficacy and geosynthetic tension is however reduced as a result. The
extreme and difference settlements and soil arcing ratio of column supported
embankment is however increased. Numerical studies demonstrate these results.
Pile Stiffness
A rigid pile is assumed by the current empirical design methods used for the estimation
of load transfer. The effect of the pile stiffness to the load transfer is hence ignored.
The effect of the pile stiffness can be calculated through the numerical analysis. Han
To study the effect of the specific parameters, it was better to assume that the above
boundary conditions exist. The simulation of the model in proximity to reality is still
a question. The presence of a hard rock stratum or rock layer at the required depth is
not always possible. Hence in this case, the toughness of the soil at the bearing layer
is also an important factor of consideration. The question whether the embankment
needs to be designed as head settling pile or a non-head settling pile may rise. The
determination of the type of embankment settlement and the geosynthetic strength will
definitely be effected.
Figure 31: The influence of pile stifness on the stress concentration ratio, geosynthetic tension and
differential settlements (Gangaakhedar, 2004)
Geosynthetic Stiffness
But Sovulj (2005) observation was in contradiction to the above. According to his
observations, as compared to combination not using the geosynthetic membrane on the
embankment load transferred to the piles, the effect of the arrangement with the
geosynthetic membrane was negligible. In addition, when the shear strength of the
embankment fill was relatively high, there was almost no effect of the geosynthetic
membrane. Suleiman et al (2003) reached to similar results in his 2D plane strain finite
analyses. The researchers concluded that in case of using the geosynthetic membrane
or not using the geosynthetic membrane, the difference in the maximum and
differential settlements of both of them were negligible. In addition, loads were also
not transferred to the piles by the geosynthetic membrane. The stress concentration
ratio also seemed unaffected. The settlement behaviour seemed more affected by the
number of geosynthetic layers as compared to the values of the geosynthetic stiffness,
provided that the tensile stiffness was more than 1000 KN/m.
Studies related to the effect of the soil models to the enactment of a column supported
embankment are absent. Various studies applying the various soil models are found
though. The load transfer mechanism should be variable according to the varying
assumptions for stiffness and yielding behaviour of soil applied in the different soil
models. To further explain consider the Mohr Coulomb model. This model provides
various stress fields due to arching in comparison to the advanced models, as it uses
one stiffness for the entire soil, while the advanced soil models use the stress level
dependency. This implies the usage of a variable embankment load transfer as well.
Studies are still required to understand the extent to which these models are different.
Figure 32: The influence of embankment fill friction angle on the efficacy (Jenck et al, 2007)
There are various trainings about the effect of the soil constraints on the enactment of
the column supported embankment, as opposed to the soil models. The effect of the
soil toughness and distention angle to the load transfer mechanism using the 3D finite
difference analyses was studied by Jenck et al., (2006). A lower efficacy was obtained
when using lower soil stiffness and a lower dilatncy angle of an embankment. It was
also observed that the compressibility of the lenient soil had no effect on the load
transfer as the pile is rigid.
The amount of load transfer is determined by the shear strength soil parameters, as soil
arcing is compelled by the shearing mechanism. The effect of the embankment soil's
effective shear strength to the embankment load transferred to the piles was studied by
Sovulj (2005). When stronger soils are used for the embankment fill, the embankment
load transferred to the piles is higher. In the same manner, Jenck et al., (2007) also
found that the efficiency will be the highest, when the friction angle is also the highest
used. The increase in the efficacy is however not directly comparative to the upsurge
in the friction angle. If the friction angle was more than 30 degrees, the increase in the
efficacy was negligible. The recommendations of Hewlett and Randolph (1988) were
further strengthened through these findings. Rendering to them, the resistance angle of
the material used for the embankment fill should be at least 30 degrees.
The similarity in the effects of the embankment soil parameters on the settlements and
the consequence of the embankment on the load transference is consistent. The
maximum and differential settlement at the embankment surfaces was lower, as the
soil strength parameters and the soil stiffness was high.
Figure 33: The comparison between 2-D plane strain and 3-D analyses (Kempton et al, 1998)
Diverse readings have been conducted to study the diverse behaviour of soil arcing
effect from 2D and 3D studies. The load transfer and settlement behaviour was
compared by Kempton et al., (1998) through a comparison between the 2D plan strain
and 3D analyses of the quarter cell embankment. The results showed a difference in
the magnitudes, although similar tendencies were depicted. As compared to the 2D
analyses, the 3D analyses showed a much lower soil arching ratio with respect to the
H/s. In the 3D analyses, higher maximum and differential settlements were observed.
The consequences of the soil arcing ratio from the 2D and 3D studies are shown in the
figure above. As the amount of the columns is lower than those used in the 2D plane
strain, the results obtained are accurate. Sovulj (2005) also showed similar results
through the comparison between the 2D axisymmetric and 3D analyses. In the 3D
analyses, the considered extreme deformation of the embankment surfaces and
difference deformation are higher. In addition, Jenck et al., (2006) also showed the
possibility of observing the horizontal pressure and drive of the embankment when
using the 3D half slice of embankment model. On the contrary, 2D plane strain analysis
was also successfully used by Zaeske (2001) in combination with the conversion
method suggested by Bergado and Long to approach the 3D analysis.
There are only a few studies done on the parameters of embankment on floating piles.
This is because most of the parametric studies discussed earlier are comparing or
improving the design from the existent empirical methods, while using the numerical
analyses results. End bearing piles are considered by most of the existing empirical
methods. Hence most of the numerical analyses are done on the embankments on end
bearing piles. The lack of knowledge and assurance on designing embankment on
floating piles may be one of the reasons. But still the construction of embankments on
floating piles is used.
Figure 34: Distribution of pore water pressure in clay at the centre of piled embankment (a)
immediately after construction (b) after 2 years)
Miki and Nozu (20040 have attempted to study the floating column type foundation.
The finite element plain strain analysis was used in the study. The columns are
entrenched to a depth of 12 m below the surface of Bangkok lenient clay with a
thickness of 20m. The effects of the usage of floating piles on the deformation of
lenient ground surface and pore water pressure change has been the main focus of these
studies. This is a consolidation type analysis. This study has not considered creep and
geosynthetics have not been applied. According to observations, the construction using
the floating piles showed significant improvement in the soft ground surface settlement
after a month as compared to that without piles.
As time passes, the percentage of improvement between the two cases will also
increase. It is only in the clay below the floating piles that the excess pore pressure
will occur. This will however reduce after 2 years. There is no effect on the lenient soil
surrounding the floating piles, when the embankment loads are used.
Across the river crossings, for a light rail line, the edge was to be built over soft
compressible soils. Due to time limitations, the traditional approaches for developing
wall over soft soils (i.e., surcharge loading and wick drains) were not feasible for this
assignment. A new skill was recommended by the Bechtel Infrastructure Corporation,
the project vendor's design-build contractor to enhance the foundation soils. The new
edge was supported by the VCC (Vibro Concrete Columns), a sister technology to
stone columns. The specifications of the VCCs were 7 to 9 foot triangular spacing. For
shifting the embankment loads to the VCCs, a geo-grid reinforced LTP (Load Transfer
Platform) was planned. With the help of a concrete modular retaining wall system (i.e.,
T-Wall), the edge was maintained along the LTP length. The design strategies, quality
standards of VCC, the post development performance along with the selection of
productive soils will be analysed in this case history.
6.1.1 Introduction
A dynamic trip of Rancocas Creek to facilitate the Conrail freight trains along with the
New Jersey Transit light-rail passenger trains has been offered by the new Rancocas
Creek railroad bridge. Since, due to worst conditions and non-functional swinging
mechanisms of the present swing span link, the engineers have developed the new
effective bridge. For a latest light rail line expanding from Camden to Trenton and
New Jersey along the east coast of the river Delaware, the new Rancocas Creek Bridge
is believed to be one of the key structures. The public of Central New Jersey will be
facilitated by the 34 mile long southern New Jersey Light Rail Transit System project
and it will offer better transportation to many regions, such as the rail systems
extending to the New York City to the north and the Philadelphia and adjacent regions
to the south and up to Trenton area
The hallway of the centuries old Camden & Amboy Railroad believed to be
constructed in 1830s will be observed as a project path. Since there was an established
route because of the alignment, however, there were certain development problems
that became impediments to achieve the required passenger ride quality during
operations within the restrictions of a current apprehension and tailored customizations
to the perpendicular and parallel configuration. Representing the southern bank to the
Rancocas Bridge, the design and development of the retaining wall system is described
by this study. While this attempt was almost the same horizontal setting like the present
arrangement, almost 20 feet upward rise was observed in the shape, and dual tracks
were introduced instead of the old single track and widening of the existing wall was
also suggested. There is a poor accessibility to the bridge because of inadequate right
of entry to the site along with undesirable soil situation and it made the experts think
to develop a novel idea so that easy access to the bridge is ensured.
Site Conditions
The Potomac Formation soils have triggered this project and it is situated across the
geographical regions of the Atlantic Coastal Plain. The Potomac contains the
acceptably uneven powder and is considered as a non-aquatic flood plain deposit and
in this zone it is naturally found nearly 150 feet dense. The main streams passing
through the area are most likely to diminish the cover of Potomac soils that leads to
the creation of wetlands and swamps adjoining the estuaries and streams along with
the removal of current muddy soils.
There is a century old soil embankment with its top altitude a little beneath Elevation
of (+ 10) feet is situated beside the entry to Rancocas bridge. While for the purpose of
holding two tracks, the embankment was primarily constructed, however the
recommended configuration had extended the old embankment to the eastern side and
intimidated the contiguous swamps due to a plane swing of the new track which was
to improve riding quality for the light rail passengers and radius enhancement along
with the loss of the timeworn embankment.
Across the project location, the three distinct phases are likely to execute the below
ground explorations, which commenced during the early design and ongoing through
the further thorough studies that are conducted for the retentive wall substitute. Up to
105 feet deep, the resources have observed 29 bores. The undisturbed soil sampling,
standard penetration test sampling and the deployment of ground water observation
wells are contained among the boring drills. Corresponding to the elevated drift levels,
the ground water levels were discovered to be as sharp as EI +3.0 feet. The
manufacturing attributes of the soil were determined by conducting the lab tests. The
moisture content, grain size, organic content determination, chemical analysis (pH,
chloride, and sulphate), Atterberg Limit, tri-axial strength and consolidation are the
different experiments included in the tests. The table in conclusion will illustrate the
soil features settled for the design management.
Since the arrangement approached the marsh and wetland areas adjoining the southern
bank of the Rancocas Stream, so a considerable change in the value of the near surface
underwater conditions has been discovered by the belowground study plan. The soil
profile consisted of 2 to 8 feet of manmade fill nearly 800 feet south of the southern
edge of the stream from the present railroad bank that is covering a medium dense silty
fine to medium sand about 18 below per foot with standard penetration struggles.
Fewer than 25 to 30 feet depth below the ground surface, these materials became
extremely thick from the thick state. A series of recent alluvial layers were discovered
from this point to the north and total thickness of these layers were enhanced to about
25 feet, since the placement relocated the stream's bank. An average silty layer, also
the sand covering layers of organic silt, peat and silty clays collectively shape these
alluvial layers. These materials were found highly compressible and lower in strength
according to the findings by laboratory. Without the capacity for slope strength failure
and undesirable settlement, it was revealed that the supplementary loading of the
sophisticated embankment could not be carried by these materials according to the
stability and settlement analyses.
Project Requirements
A seven span viaduct spanning over the soft flexible soils under the old bank located
south of Rancocas Creek was included in the early design for accessibility to the new
Rancocas Bridge. The concrete-filled pipe heaps pushed through the light soils into
the dense beaches were included in the foundation for the overpass. The precast
concrete bridge beams would be carried by the pile caps at each bent so that the direct
fixation track could be effectively supported. The design specifications of the project
including the sustainable support were fulfilled by this viaduct, and for the outer track
of flexible soils it had the soil-to-structure transition along with no settlement for the
bridge access. However, in the developments of highways, the demand to avoid "bump
at the end of the bridge" is judgmentally vital in the developments of railroad so that
the compact at this evolution from developing in the rails may be prohibited due to the
extreme strains.
Regarding the viaduct, it was revealed by the calculation of construction series that
each pile cap and pile foundation would likely to be commenced from the southern
edge of the river in a consecutive way. Basically it is required to create the pile caps
above the existing grade, because of the fibre optic cable which could not even be
displaced, hence causing inconvenience at the location. The development of access
roads for comforts neighbouring the work location was not allowed as a result of
ecological constraints and the restricted entry. Furthermore, because of the big lifting
radius for the 60-foot long beams, a 500-ton capacity crane is engaged for the
settlement of the 80 to 100 ton bridge beams from every distance. The time lines get
extended and costs got overran from the budget provisions in a considerable way due
to the blend of the tools requirements and the construction sequence. Accordingly, a
substitute was likely to be sought by exploring the value engineering study.
It was rapidly explored by the value engineering study that to hold the desired twin
tracks among the limited access described by the nearby swamps, a retaining wall
system would be needed. There were certain replacements, which were determined on
the basis of general needs, comprising a planning and development budget equivalent
or lesser than the viaduct alternative, the construction techniques for a narrow site area,
a robust and constant retaining foundation principally free from post-construction
settlement. The wick pipes were likely to be administrated by the soil enhancement
techniques and these approaches soak due to the expected post construction settlement
amounts and reasonably unnecessary time for equilibrium. Because of schedule and
cost factors, construction of cast-in-place concrete was governed by the analyses of
retaining wall design and construction techniques; however, it was not uncovered that
to fulfil the strengthening requirements in order to supporting the rail road freight
loading and light-rail, a retaining wall system was desirable or not for the large precast
concrete components.
The T-WALL Retaining Wall System was chosen after the comparison of various
retaining wall systems. It is basically a T-shaped precast enabled with concrete
materials and is also referred to as a gravity system.
The benefits regarding the substitute retaining wall and the ground developments over
the viaduct choice was analysed and confirmed through the construction schedules and
through the preparation of cost estimates. The ground improvement selection
techniques along with other dynamics were approved for further enhancement.
The finished railroad track structure needed to be settlement free so that undue stress
may be avoided from developing in the rails, while due to the construction design,
there had been a tremendous flexibility to accommodate settlement by the T-WALL
retaining wall. Attributes of the original grounds were used to conduct the settlements
analysis of the projected approach so that the estimates of the total settlement can be
presented. It was expected that there would be a long settlement period due to the
sustained density of the peat soils and the maximum calculated settlement was nearly
24 inches.
The transmission and distribution of the load to the VCCs from the retaining wall is
one of the major features of this system. During design, it was decided that the
construction approvals for the VCCs and T-WALL would disallow the direct support
of the precast elements on the top of the VCCs. The possibility of a concrete pile cap
over the VCCs was not allowed by the schedule and cost factors, and the occurrence
of the load distribution would not be allowed by the strength of the pile cap.
Hence, on the basis of almost hundred ton per column, the features were checked for
structural capacity. With the help of dense graded aggregate back fill, the dead weight
of the T-WALL concrete sections, the railroad loading of 2000 pounds per square foot
these all are desired to determine the loading capacity.
The Hayward-baker Company successfully deployed the VCC and with infiltration of
the vibrator, no difficulties were reported. Its columns are configured triangularly and
there is a 7 to 9 feet spacing range of the VCC. It took less than 3 weeks to deploy the
625 VCCs reaching over 60 columns per day and with desirable optimum output.
The materials are supplied from behind the vibrator rig through the usage of pumped
concrete so that blocking in the work area can be decreased. A low fall of 4, 000 pounds
per square inch pump-able concrete was chosen due to acceptable load capacity of 200
kips and the ready mixed suppliers certified by the State of New Jersey DOT are
authorized to produce the same. Since, there was no air based activity with the concrete
and it was pumped into the ground, and the accelerators for winter condition were not
A nineteen inch vibrator coupled with a concrete pump line was operated to deploy
the columns, and concrete was allowed to be pumped to the bottom of the vibrator
through this mechanism. The accomplished VCC was believed to be having an
estimated diameter of about 20 inches and on the other hand, due to some squeezing
of the softer soils, there is a minimum size of about 16 inches. The extended vibrating
times at the bottom are offered by the construction methods and these techniques
provided column to grow the top and base both to as much as 30 inches. (For the design
matters, a column expression of about 24 inches was considered).
An electronically driven bottom feed vibrator is utilized by the VCC procedures, from
which weak sub-soils are infiltrated to a level with either adequate bearing ability or
to coarse grain soils which can be enhanced and compacted through the pulsation. The
weak organized and organic soils were displaced while rough layers were strengthened
by the vibratory actions during the initial penetration of the vibrator. The concrete
pump was switched on, introducing concrete from the vibrator tip in to the ground,
when the development of the load bearing formation was complete and the vibrator
was initiated to begin the column construction process so that, at the base, a bulb of
concrete could be established. Then the concrete pressure was maintained, whereas the
vibrator was slowly withdrawn and eventually a constant concrete shaft up to ground
level may be formed / produced.
The procedures and dynamics of Quality control for VCCs are diverse and following
are thought to be contained in this process, such as: materials testing and verification,
the selection of qualified personnel, load testing and compliance to well-known
construction procedures. Although, till date, North America has not significantly
observed the VCCs, but, skilled field personal with hands on experience using obvious
depth vibrators and the various suppliers have employed vibro replacement systems
like stone columns over the past 1 quarter under different projects. The firm adherence
to pre-assigned construction procedure as already mentioned is one of the most
important aspects of quality control on the VCCs construction. For itself, appropriately
skilled staff should be considered for the implementation of any such project. Each
VCCs was recorded as a fundamental portion of the procedure on a vibro concrete
column record sheet that contained, start time, depth, end time, column location,
amperage, maximum vibrator, concrete volume pumped, unusual observation, average
pumping pressure and comments regarding any changes.
In compliance with ASTM 31, four concrete cylinders were moulded on daily basis
and it was validated by production concrete strength, and 5, 10 and 28 days operations
were performed where the tests were conducted in line with ASTM C39. A load test
column was nominated to verify the capability of the VCC design, once various
production columns where finished in line with the recognized construction
The mathematically load testing one column is included in the load test program.
Generally, in line with ASTM D1143-81 the compression static load test was
performed "standard test method for piles under static axial compression load" and
when acquisition of the requisite amount of strength was reported by the concrete, then
it was initiated after a complete break test. The summary plan of load versus settlement
is illustrated in the figure below. The normal vertical movement of the test column butt
at each load increment is encapsulated by the load versus average test column butt
deflection. The test results are covered by the theoretical elastic compression line and
the failure criteria (i.e. Davidson criteria) so that the test columns output regarding the
theoretical density line could be demonstrated in addition to the failure criteria at each
load increment.
Up to a higher test load of 300 kips or 150 % of the design load was applied with
respect to the compression load test. The whole movement of the test column butt,
0.46 inches, was found less than the 0.48 inches identified failure criterion of the
design compression load at 300 kips or 150 percent. After unloading, the net set was
found to be 0.24 inches. The VCCs satisfied the criteria for a design compression
capacity of 200 kips on the basis of the findings of the firmness load test.
Settlement monitoring was conducted on levelling pad deployed at the base of the T-
WALL to offer verification of the criteria in the performance specs. In March, 2001,
after the completion of the T-WALL construction of the backfill, a set of the reading
were recorded along the east and west walls. After 3 months to the prior reading, the
next set of reading was observed and a maximum settlement of about ¼ inch had been
noticed. This settlement was considerably less than the allowed settlement, so the
authorization of the VCC's output and the load transfer platform has been presented.
It was the journey of one year to manage the southern access and the new Rancocas
Bridge. No supplementary twist of the support system has been reported by the
additional settlement survey that was conducted after one year.
6.1.6 Conclusion
While the speedy construction over soft soil is desirable, however these construction
periods are satisfactory for the railroad construction and the highway departments. The
rapid construction can provide faster opening of the facility is offered by the quick
construction so that the troubles for both the public and business could be minimized.
The site that has been selected for the purpose of placing a pile supported embankment
is located on Trunk Highway (TH) 241 in the vicinity of St. Michael, Minnesota which
is about 610 m southwest of I-94/TH 241 interchange. The area of TH 241 that was
selected for the pile supported embankment was in between stations 167+50 and
Figure 39: Map showing project site in relation to St.Michael and the twin Cities.
The entire area was assessed to find out the terrain and the geographic features of the
area so as to implement the system accordingly. It was evaluated that the highway was
bordered with a small pond to the northwest and by a marshy terrain on the southeast.
The foundation for the westbound highway was developed using load transfer platform
(LTP) as shown in. Since the west side is being used for the purpose of embankment
building the soil on the west has been tested by boring at station 169+65.74. The boring
was done till well-cemented sandstone was found at a depth of about 30.5 m below the
surface. It was evaluated that at a depth of 9.1 m highly organic silt loams were present
and around 6.1 m below the silt organic soils were found layers of peats. Underneath
it was a 3.7 m of loamy sand caused by a 10.7 m of gravel sand.
The two way highway built on TH 241 in 1938, repaired for the first time in 1955/
1956 and then again repaired in 1973 by multiple layers of bituminous resurfacings
but the soft soil present beneath this construction was not catered during any of the
renovations and highway expansions and extensions carried out; as a result of which a
much visible dip could be observed in the highway section which is expanded over
107 m. The merging of the embankment and the highway could easily be observed
before the 2006 extension of highway took place.
At the time when the highway was built, the traffic was quite minimal in amount but
with the passing years St. Michael area has been developed to quite an extent and a
noteworthy increase in residential, commercial and industrial traffic can be observed.
It has been expected that development in this area will continue to cultivate and the
traffic will increase up to 90% between the years 2005 and 2025. This increment in
the traffic has led MnDOT to make a decision of expanding the highway from two
lanes to four lanes so that the increased traffic can easily be taken care of.
The merging that took place for expansion between the highway and the original
embankment was slightly below the embankment and not along the edges which
resulted in considerable amount of differential settlement between the two regions and
this was a matter of great concern. In order to overcome this problem a number of
solutions were considered among which some of them were the use of a land bridge
along with the repositioning of the road and using of a fused foundation structure
comprising of a pile supported embankments. The latter solution was considered as an
effective and feasible solution and was implemented. During the process of expansion
it was found out that the soil of the southeast side was much softer and shallower than
the soil of the northeast side. To cater this issue MnDOT presented the idea to make
use of a conventional shallower foundation. The process was to be carried out by first
quarrying the soil, then loading it in order to speed up the process of merging and
finally making use of geofoam light- weight filling so that the loading could be
reduced. This geofoam used had been spread over the entire highway up to the base of
the column supported area. The cross-section of the expansion design has been
illustrated in figure below.
The expansion and merging process and the implementation of the solution presented
for reducing settlement, the process of testing starts. The area of the pile supported
embankment that had been selected for placing the instruments for testing was in the
southwest end, located in between stations 168+00 and 68+50; this has been shown in
the figure in previous page This area was particularly selected for two reasons; one
being that this area had considerable isolation from the BSNF rail road which produced
strong vibrations that could certainly have adverse effect on the measurements. The
other reason was that the embankment was the thickest in this region and thus provided
the largest loading effect and this helped to minimize the errors that could arise in the
The area to be tested is located beneath the highway section of the embankment not
underneath the reinforced slope. In order to obtain measurements accurately it would
be better and more preferred to place the sensors at a location that has uniform
distribution of pressure and loading and the vertical stress and strains could be easily
calculated and predicted. Thus, it can be concluded that this area had preference for
getting selected because it has uniform distribution of load.
To carry out the test process the piles were divided into two groups of six piles called
unit cells. This process of dividing the piles in to two groups was carried out to obtain
redundant data. Unit cell1 was composed of semi-hexagonal area including the piles
7029, 7003, 7032, 7033, 7036 and 7037, whereas the unit cell 2 comprised of semi-
hexagonal area including the piles 7043, 7044, 7046, 7047, 7050 and 7051 as can be
seen in figure below. The sensor placements in both these cells were almost identical
so that the measurements obtained from the two cells could easily be compared. The
sensors used in both the unit cells were slightly different so that different sensors could
also be tested, for instance vibrating wire earth pressure cells were used in unit cell 1
whereas semiconductor based earth pressure cells were used in unit cell 2.
Sensors and other instruments being used for testing were placed in four different
locations namely the piles, the base and
the top of Load Transfer Platform (LTP)
and the geogrid layers. Summing up all the
sensors used, 48 sensors were placed all
over the platform and the piles. Besides
this 12 EPC's, 6 settlement systems, 20
strain gages on the geogrid, 2 of them on
the piles and 8 of them on the pile walls.
The following section includes the detail
of each sensor used along with the reason
of selecting their location.
Figure 42: A plan view of the instrumented region of LTP.
In order to place the strain gages for measuring pressure, four different piles were used
namely P1-P4 (points 7029, 7036, 7043 and 7050) which lie on the same streak in the
grid and are parallel to the highway. The strain gages that were used were axially
placed on to or in to the piles. A total of three different types of strain gages had been
used for the purpose of testing. One of the types include concrete embedment gages
(model VCE-4200) comprising of vibrating wire operating principle. The different
parts include the coil housing attached to the cable and this arrangement is removed
from the gage during the process of installing and is finally placed during the last stages
of the process; The gage was bought from Geokon Inc.
Figure 43: Diagram showing components of vibrating wire concrete embedment strain gage.
Two of the above mentioned stain gage models were used and implemented on to two
different piles specifically P2 and P4 and after the placement were branded as P2C and
P4C. In order to pour and cure the concrete into the piles, it must be made sure that the
piles are erect and maintain their position. For this purpose to steel rods were fastened
to the walls of the pile so as to mention the pile shape. These rods were placed
horizontally having a gap of six inches with the intention to strengthen the base as well
as the top of the piles. This entire arrangement has been clearly illustrated in Figures
below. To carry out this process, the first thing that needed to be done was the drilling
of the holes on the side walls so as to support the steel rods. Then the concrete mixture
was poured into the pile walls and they were filled till the level rose to 2 or 3 ft. beneath
the top. Then the rods were placed in to the holes and tightly fastened to the walls. The
rods used also provided support for the strain gages and helped in the placement of the
gages in the centre of the pile. The base was then fixed to the rods and holes were
drilled so that the cable from the coil housing could be connected to this pile. At the
end, the piles were filled with the left out concrete with hands so as to provide no
damage and harm to the gages.
Figure 44: Plan view and perspective view of concrete embedment gage installation
The other types of strain gage that had been used for the purpose of testing were the
Micro measurements EA-06-250BF -350 (option LE) foil (resistive) strain gages. As
mentioned above, the piles P2 and P4 were installed with the Geekon 4100A-2
vibrating wire strain gage and the remaining piles P1 and P3 were installed with the
EA-06-250BF-350 strain gages. All he strain gages were placed 12 in. (30.5 cm)
beneath the upper portion of the pile. The gage placement was perpendicular to the
highway line. This complete installation has been depicted in Figure below.
The filling of the piles with concrete mixture takes place before the gages are placed;
this caused the surrounding area to get dirty with the splashes of the concrete mixture
being filled. Therefore, the surrounding area is made clean before the gages are placed
so as to ensure the safety and protection of the gages. A number of different bonding
agents and protectants have been used for the two types of strain gages used. The foil
gages made use of a cyanoacrylate (Micro measurements M-200) for attaching the
gage to the pile wall. The gage must be protected from water and moisture in order to
make the gage work accurately and give correct results. For this purpose the gage and
the wiring is sealed and a water proofing kit (Micro measurements M-Coat F)
encompassing butyl and neoprene rubber sheets along with a foil tape and a liquid air
drying nitrile rubber coating is used. This arrangement can be seen in the figure below.
The vibrating wire gages made use of spot-welder for attaching the gage to the walls.
The gage had been provided with mounting tabs and these tabs were welded on to the
walls. In this case cyanoacrylate adhesive had been immediately applied after the
welding process for the protection of the gage from corrosion. The vibrating wire gage
has coil housing along with a cable placed just on top of the gage; this assembly was
also attached to the pile wall by welding it with the mounting strips. For the purpose
of securing he gages from any harm, the gages had to be sealed. The sealing of the
gages were carried out by making use of a caulk design with steel was spread on to the
edges before and after welding. To provide exterior protection to the gages from
getting detached or getting displaced from their position the cable from the coil
housing assembly was enfolded around the pile and then fortified to the wall. Lastly,
all the cables were connected to the data collection box after the cables were passed
through a stretchy duct.
Figure 47: Spot-weldable vibrating wire strain gage installation on pile wall.
Sensors have been placed beneath the Load transfer platform (LTP) because the
sensors have been placed erstwhile the placement of the partition fabric. The base of
the load transfer platform which is at same level as the pile cap had been provided with
twelve sensors, among which eight sensors were earth pressure cells and four sensors
were used for settlement systems.
A large variety of earth pressure cells are available but in this project hydraulic type
earth pressure cells have been used. The arrangement of these cells has been explained
in detail in this section. Two thin discs are first welded together at the edges leaving a
small gap between the discs so that the liquid or the fluid can be filled up in the gap.
Then this fluid is connected to the pressure transducer by means of a short duct. This
arrangement can be seen in figure below. The fluid that is filled in the gap is
considerably an incompressible fluid. The process of measuring the pressure is quite
simple; the loading on the outer surface of the discs exerts pressure on the fluid filled
in the gap which in turn causes the pressure transducer to measure the pressure. This
pressure measured by the pressure transducer is assumed to be somewhat equal in
value to the earth pressure at the face of the cell.
For the accurate measurement of the pressure it was desired that the cell being used
must be under significantly uniform pressure distribution which would otherwise lead
to errors in measurement. In order to reduce the chances of error in pressure
measurement the diameter of the discs being used should be small. Although the
commonly used diameter size of the disc is 22.9 cm but for this case in order to get
accurate results discs having diameter of about 11.7 cm is used.
Moreover, as discussed earlier the piles had been divided into two groups with slightly
different sensing elements used in each set, for the purpose of getting redundant data;
earth pressure cells having two different sensing elements were used for the two sets.
With one unit cell vibrating wire pressure transducers (Geokon model # 4800-1X-
170KPA) were used whereas for the second unit cell semiconductor based pressure
transducers (Geokon model # 3500-1X-160KPA) were used. For any sensor or device
to be used for measurement it is a necessary condition that it is calibrated according to
the conditions in which it is to be used of measurement. Likewise, the earth pressure
cells were also calibrates according to the soil conditions.
In order to obtain better and more accurate results earth pressure cells have been placed
in four different locations of each unit cell. Two of the earth pressure cells were placed
at the centroid of the triangular pile assembly while the remaining two earth pressure
sells have been placed at the midpoint of two neighbouring piles. The latter position
had been selected so as to provide a check for arching. The load due to the overburden
on the platform causes very high pressure at each location of the piles but due to the
presence of arching this large amount of load gets transferred to the piles and the
measured value of pressure considerably reduces. In order to minimize the effect of
local stress the sensors are placed at a distance from each other so that the local stress
factor does not get included. The similar setting and arrangement of the sensors have
used in the second unit cell so as to obtain redundant data and measurements.
The procedure of implementing the earth pressure cells on to the piles has been
explained in detail. To place the earth pressure cell a hole was dug in which the soil
similar to the one that had been used during calibration is filled and compressed to
attain similar conditions which were taken during calibration of the cells. After the
desired conditions and surroundings were achieved the earth pressure cell was inserted
into the soil, levelled ad then again covered with another layer of soil. The cables after
passing through an elastic tube were connected to the data collection box from which
the first measurements were observed.
The two different types of sensors that had been used were the vibrating wire earth
pressure cells and semiconductor based earth pressure cells had similar parameters i.e.
11.4 cm diameter and matching capacities of about 170kPa and 160kPa respectively.
It has been mentioned that the earth pressure cells have been situated near the base of
the piles. This is done so considering the results obtained from the earlier researches
by Rathmayer (1975) and Reid and Buchanan (1984) in which it had been concluded
that the pressure distribution at the top of the pile is strongly varying, with pressures
near the edge being greater than the average pressure and at the centre of the pile cap
to be less than the average pressure. For the measurement it is expected that the load
above the pile cap would be equal to the load on the piles and thus the pressure reading
could be taken much more accurately.
Settlement Systems
The sensor positioning was selected on the basis where maximum displacement could
occur and it was found out that the position where the earth pressure cells were
installed had the maximum chances of displacement. The area above the pile caps was
found to be least affected by the shift in settlement systems and it was perceived that
there will be a shift only because of the dislocation of the piles; therefore, the sensors
were placed at the location of the earth pressure cells with slight offsets. The offsets
were introduced so as to minimize the effect of the surroundings. Shift at any other
location would be insignificant.
The fixing up of the settlement system was quite similar to the installation process of
earth pressure cells except the dumping of sand was not necessary and the lines needed
to be connected to the reservoir as soon as the setup was ready.
At the top of the load transfer platform six different sensors have been employed. It
had to be investigated that load transfers or arching could take place at the platform or
not. It was predicted that if arching occurred within the platform the pressure
distribution would become considerably uniform. For this purpose two of the sensors
used were the earth pressure cells which were installed in each unit cell, one of which
was placed at the top of the pile and the other at the centroid of the assembly. The
settlement system was also places at this same location but with the slight offset due
to the same reason mentioned in the previous section.
126.96.36.199 Geogrid
Strain levels in the geogrid were measured using foil strain gages. The various gages
are installed on to the grid in the laboratory in the form on an array. The array
comprises of 10 gages placed at five different locations such that they remain parallel
to the highway and aligned over pile P2; this helped to obtain redundant data. Two
different gages have been located at each position such that one of the gages is parallel
to the highway (marked as 'L') and the other is perpendicular (marked as 'T' for
transverse). The gages were so arranged to obtain a complete overview of the pressure
from the pile to the centroid of the entire assembly so that the pressure distribution
could be determined along with the position where maximum pressure occurs
For the installation of the gages that was method was adopted which could provide
support and maintenance (Warren et al. 2005). The process included the cleaning and
levelling of the surface because the surface was initially quite rough. For the gage to
remain intact with the surface a silicone adhesive (Dow Corning 3145) had been used.
After that the gage was placed at the desired location and then left under pressure so
that it could firmly stick to the surface. After that the same adhesive was used for the
purpose of water proofing. M-Coat B was also applied before and after the application
of electrical tape for further protection. This has been illustratively shown in figures
The entire data collection system has been caged in a box and placed at the base of the
embankment. Reservoirs were also enclosed within this box so that they can be used
as a benchmark for the readings. It is ensured that the box does not displace during the
process of measurement so that no errors can arise and the only movement that the
transducer detects is that of the sensor. There were chances that the box at the base
may result in some sort of settlement issues; therefore to cater this problem the box
was supported at each corner by a 3.7 m long 10 cm x 10cm wooden posts.
During the course of the construction, testing and data collection a number of problems
and issues arose. Among these problems some were petty issues and were easily
handled but some had serious impacts on the project and could not be eliminated. Some
of these issues have been discussed below.
One of the serious issues that had to be faced was that after the installation process
was complete data obtained from some of the sensors were lost.
Pile Gages: A number of gages were misplaced including four foil strain gages,
one vibrating wire strain gages, and one embedment gages. Some of the initial
readings that were obtained were also ambiguous and could not be taken as
final readings.
Strain Gages: Some of the strain gages were not strong enough to survive the
tests and two of them could not even survive the initial laboratory tests, 10 of
them mostly located on geogrid layer 1could not survive the field installation.
Settlement Systems: Measurements obtained from one of this system was lost
during the process of installation.
Another problem that had to be encountered was that the data collection box was
placed after the installation of some of the sensors; as a result some initial readings
could not be taken although a few of them were taken manually. This happened
because of lack of communication with the contractor, weather conditions, and the
pressure to stick to the schedule. Installations of sensors took much time which resulted
in negligible time for setting up the data collection system. Proper measurements
started after the installation of load transfer platform.
In the region of Bangkok, a bridge namely, the Wat Nakorn-In Bridge on the West
Bank of Chao Praya River along with a consecutive road system was planned for
building for the convenience of the traffic blocking; additionally it comprised of a huge
network of interlinked roads those were considered helpful in the erection of other
various small bridges along with traffic overpasses and this project was referred to be
one of the mega structure projects. This bridge was planned to develop by including
passages for Nonthaburi bridges and Rama VII. This mega structure project was so
huge that it has to be proportioned into five distinct contractual agreements in which
each of those contracts comprised of erection of embankments and bridges to organize
around 10 traffic ways.
Figure 49: Constrution of Wat Nakorn – In bridge Approaches, Bangkok (Tencate, 2013)
In order to accomplish this mega project, the groundwork was initiated by putting a
hard layer of "soft Bangkok clay" with a depth of around 15 to 20 m of the Bangkok
metropolitan area; this kind of clay was utilised as it is extremely compressible with
very squat shear potency while a little bit strengthened. One of its positive points is
that it has water contents of about 80% to 140% replenished shear potency from 6 kPa
to 15 kPa while its bulk densities were put in accordance with 14 kN/m3 to 16 kN/m3.
Figure 50: Typical long section through the basal reinforced piled bridge approaches (Tencate, 2013)
Huge differential settlements among the embankments may occur by the merging of
the soft clay which was further constructed unswervingly on the piled bridge structures
and on the clay. Actually these differential settlements serve to cause certain shelter
vulnerability while diminishing the riding quality. In addition, they require
maintenance very recurrently which tend to be of very high cost consumption along
with generating irrelevant traffic blockages and obscurities as the roads will not be in
use for the accomplishment of maintenance.
linked with the embankments. A smooth road's construction can be ascertained with
this tapering of pile depth from the segments that are not sustained by piles while all
the other embankment segments are sustained through these piles formation across the
bridge structures. .
In order to initiate this erection of mega structure, the surface vegetation was
eradicated from the construction site while the concrete piles of 100 mm square were
underlined along with the design depths with utilising drop-hammer piling machines.
The gaps of 1 to 2 m were given besides the embankments which rely on the distance
from the bridge. Afterwards, in order to give support, connecting beams and pile caps
were built on the zenith of the piles; the connecting beams were comprise d as the soil
that was laid in the beginning was very malleable while it was preferred that additional
lateral restraint was necessitated for the objective of permanence. Subsequently, the
pile caps were later on
backfilled and the connecting
beams were merged with sand
in order to outline a horizontal
Consequently, the sand fill was placed and compressed on the embankments as they
were needed for design heights.
In the district of bridge abutments, the
embankments were had to build with
steep side slopes with the utilisation of
Miragrid® 5XT geogrid reinforcement at
0.5 m vertical spacing in the
embankments in order to constraint right-
of-way traffic afterwards the surface of
Figure 53: Piling the embankment foundation
(Tencate, 2013) the reinforced steep slope was covered by
vegetation so that the embankment sides
can be finished up with greenery.
The embankments of low unit weight were created while utilising expanded
polystyrene (EPS) to fill in those places where the embankment altitudes were quite
squat and there was no obscurity with differential settlements and serves to diminish
the level of settlements happening in those embankments.
Malleable asphalt pavements were built up on the top after the construction of
embankment earthworks.
A mega structure project linking Northern Ireland and Republic of Ireland has been
built up in the current time creating a cross border where the segment of section of the
A1/N1 dual carriageway is constructed but it was a great deal to finish up this project
as it was full of obscurities as it has to go through the Flurry bog which is actually a
huge peat bog consisting of smooth layers of silt of around 1 kilometre long and 9 m
deep while besides the peat bog was a fixed band of gravel overlying rock.
The Flurry bog is that kind of place in
which the hard water of ground is filled
up to the surface level even this land is
that much low-lying that it has a fear of
being flooded from a nearby river, River
Salmonoid i.e. why this part of land gives
a similarity of wetland rather than being a
bog. In additio n, the peat of this area has
a very small amount of fibre potency
Figure 55: Laying Geolon® PET geotextile reinforcement
(Tencate, 2013)
which makes the availability of surface a big difficulty even it is very obscure to walk
It was suggested to construct two distinct foundation treatments in the form of dual
carriageway embankments because of its changing deepness of peat situated besides
the highway alignment even the places were dug out and reinstated with granular fill
where the deepness of peat was found
quite low. While in some of the other
areas, a basal reinforced piled
embankment solution was utilised
where the peat depth was not more than
400 m long and the piles of strong
gravel stratum were also used up below
the peat bog for this very purpose.
An internationally identified design Figure 56: Driving concrete piles through the working
code, BS8006 was taken into account platform (Tencate, 2013)
in order to plan the basal reinforced
piled embankment along with giving variations in fill height besides the piled
embankment's length. Certain alignment constraints were noticed therefore the
altitude of embankment was created with minimum criteria of 3 m above the pile caps
even additionally it was settled on to preload the embankment consisting of 1 m
supplement so that the basal reinforcement can be pre-strained while diminishing all
the long-standing confine deformations inside the embankment.
On the tops of the pile caps, a design was finalised encompassing Geolon® PET
geotextile reinforcement which was to be utilised at last while two distinct geotextile
reinforcement amalgamations were used up which were actually reliant on the
embankment altitude. In these amalgamations, one comprised of 700 kN/m
longitudinal and 800 kN/m transverse potencies while the other one encompassed 700
kN/m transverse and 600 kN/m longitudinal potencies and these potencies had to be
evaluated over the criteria of tolerable design strains, weights and necessitated life
spam of design.
This construction site cannot be sighted until a working platform was built due to the
less potential of groundwork
layer and another layer of
Polyfelt® TS80 geotextile/
Miragrid® GX35-35 geogrid
stabilisation was required to be
built for carrying on the
construction process of
reinforced working platform
transversely located in the base
Figure 57: driving concrete piles through the working platform area of the intended piled
(Tencate, 2013) embankment. Afterwards, the
working platform was rapidly
built by utilising geogrid/geotextile amalgamation which further worked to grant the
rigidity and potency needed for stabilisation which was so useful that it further
diminished the weight and required depth of the working platform while permitting
rapid indulgence of seepage ground water.
The embankment was sustained while utilising 2700 precast concrete piles which has
to be fitted over the area of 2.5 m grid with making them fixed up to 3 m inside the
gravel stratum below the peat bog. Consequently, these concrete piles were settled, the
pile caps of 0.8 m square were built on the top of the affirmed piles so that they can be
filled in the working platform afterwards in order to overlap the topmost part of the
pile caps.
Figure 58: Typical cross section through the Geotextile reinforced piled embankment (Tencate, 2013)
The embankment was constructed by cutting the highway alignment more and
afterwards filled with granular fill. Subsequently after its construction, the granular fill
was located and altered in such
a way that it become
accessible for compaction and
geometrical tolerances
inclusive of 1 m surcharge and
this surcharge is eradicated
after the time period of 6
months in order to assemble
the pedestrian area.
Figure 59: Completed piled embankment (Tencate, 2013) After finishing the project, a
comprehensive embankment
monitoring program was executed through which we reach to the outcomes that
showed a pessimistic result clarifying the unsettlement of embankment all through the
time period of monitoring. In accordance with the outcomes of settlement records, the
ground part of the piled embankment did not demonstrate any settlement on the top of
the pile cap where a settlement of around 100 mm of the geotextile reinforcement was
discovered in between the pile caps. On the contrary, these outcomes illustrate the
basic element of this technique in which the basal geotextile reinforcement collapses
among the pile caps while the transformation of an un-arched embankment loading
was possible driving on top of the pile caps.
The above picture illustrates the M74 Completion Project which consists of the last
completion phase of a motorway network in the city of Glasgow, UK. This last phase
of the project was 8.5 km long and prolongs with the present M74 Motorway situated
at the Fullarton Road to the M8 Motorway south west of Kingston Bridge next to
Glasgow City Centre. The entire route encompasses 4 huge grade-separated junctions
inclusive of a large motorway which was more than 750 m in length.
The M74 Completion Project was built transversely to the principal Brownfield land
(a place that was polluted by certain
industries of past). This motorway alignment
is located on the southern side of the River
Clyde which comprises of malleable alluvial
clay in the depth and serves as the soil used
for groundwork and the layers of these clays
are 12 to 35 m deep with partly covered with
the dense sand, rock and glacial till even a
number of foundation techniques were Figure 61: geotextile reinforcement around anchor block at
utilised due to the tense construction edge of piled area (Tencate, 2013)
programme. The plan of the project also preferred above ground construction with
merely a small length of cut.
Figure 62: Typical cross section through the approach embankment (Tencate, 2013)
Now, in the next step of the construction of this project, several primitive industrial
buildings which were located along the alignment of the construction site were pulled
down and their foundation and building wreckage was compressed in order to utilise
it in the embankments rather than setting out in the landfill as it was also preferred in
order to save environment from further pollution. Afterwards, the entire recycle
material was utilised in the construction of the piling platforms. Consequently, the
route was lined up along with an urbanized area meant isolated work sites even it was
discovered that most parts of the route were abandoned which exaggerated a number
of businesses and their operations.
Basal geosnthetic reinforcement was further used up with piled foundations for 13
approach embankments to the grade-separated junctions found effective for quick
construction and deterrence of differential settlements. In order to construct the
embankments, the internationally proven design plan of BS8006 was preferred for
constructing the embankments where ever embankment approach was planned for pile
spacing, pile cap size, and basal geosynthetic reinforcement potency and conservatory
After the installation of the piles, they were capped in a circular way, cast insitu and
concrete caps of 900 mm in diameter. The pile caps were afterwards made above 0.05
m from the usual ground level by
putting in the sand where the depth lies
between 0.05 to 0.15 m which was
useful as it provided a smooth layer for
the Geolon® PET geotextile
reinforcement located transversely on
the tops of the pile caps.
to 1600 kN/m with the tensile potencies located transversely over the width of the
embankments approach and the other layer was made utilising the Geolon®
PET geotextile reinforcement ranging from 100 to 200 kN/m with tensile potencies
and located next to the long approach embankments. The quality of utilising Geolon®
PET geotextile reinforcement was high modulus and strengthening high polyester
yarns which further result in a reinforcement material amalgamating with low
extension and creep features along with high long term potency. In addition, the
geotextile reinforcement layer was enfolded with a rectangular anchor block where the
pile embankment foundation was on an extreme level along with carrying the
embankment fill to a necessitated distance for the development of ample frictional
bond resistance in order to sustain the tensile weights which were produced the outer
Soon after the completion of the Geolon® PET geotextile reinforcement, the Zone F
high friction granular fill material was utilised to cover the top with the layers of
around 1.5 m to 2.5 m afterwards Class 1/Class 2 fill was taken into account for
constructing the rest of the embankment. Also, a regime of subgrade and surface
monitoring at the pile/structure crossing point was also involved in order to finish up
the monitoring process.
Lastly, the construction of base course, surface layers and the pavement capping layer
were finished up with certain relevant traffic subsidiary units.
This model used for analysis is taken from a case study - Ariyarathne and
Liyanpathirana (2014). Thereafter the PLAXIS results were compared with the Case
Study (ABAQUS results).
Figure 65: Embankment geometry with the soil profile (Ariyarathne, 2014)
The geometry consists of two soil layers( Soft clay and coarse grain) resting on top of
bedrock as shown in above image. The ground water table is at 1m below the ground
Multiple aspects of the numerical model are evaluated in this section, along with the
procedures taken into consideration for simulating the embankment through the
finite element methodology.
Table 3: Material properties used in the PLAXIS analysis ( finite element simulations – Ariyarathne,
by Liu et al. (2007) and Ariyaarathne (2014). The geo-synthetic layer represented was
assumed to have a greater value of stiffness towards trying to replicate the addition of
a geo-synthetic layer over a conventional embankment, with the layer assumed to be
having properties associated with linear elastic materials.
As already stated, four cases were included for the modelling application. Case 1
relates to the scenario entirely including both pile supports and geo-synthetic
reinforcements. Case 2 only considers pile supports while Case 3 studies pile
supports including inclined piles at the batter slope of the embankment. The final
case looks at the combination of case 1 and case 3 which is the presence of pile
support, inclined piles at batter slopes and geosynthetic reinforcement. Aspects of the
embankment geometry, the material parameters and the sequence of the construction
are considered uniform for all four scenarios. In modelling cylindrical piles within a
two-dimensional space, there is a need for conversion into pile walls perpendicular
to this paper. Correspondingly, multiple two-dimensional scenarios could be utilized
Ariyarathne et al. (2013) has debated multiple aspects of the situations. For the present
scenario, 3D piles are changed to pile walls by a process of equalising the planned area
related to a pile within a 3D unit cell, in conjunction to a 2D cell, towards concluding
the best case situation depending on the findings calculated. A resultant value of 0.26
m was derived to represent the thickness of the pile wall within a two-dimensional
plane-strain model, even while the pile spacing in the transverse direction remained
the same as earlier.
Considering that the soft clay layer is under the levels of water prevalent in the soil,
and is correspondingly completely saturated, it was evaluated under multiple
conditions which included while using 15-node biquadratic displacement, bilinear
pore pressure, and using reduced integration elements incorporating pore pressure in
multiple degrees of freedom at the corner nodes. The 7-node quadratic displacement
truss elements were utilized to evaluate the geo-synthetic layer, in due consideration
of the truss elements being constrained to transfer axial forces and not bending
moments. Considering that geosynthetic reinforcement is limited to only transmit
tensile forces, the creation of compressive forces within the truss elements is therefore
limited. Copying an existing case history, Ariyarathne et at. (2013) were able to
demonstrate how two-dimensional modelling utilizing the equivalent area
methodology utilizes truss elements, and correspondingly is able to influence the
characteristics of piled embankments.
In stating the boundary parameters, the x-axis is taken horizontally, while the y-axis is
considered vertically. Considering that the embankment is symmetrical to the middle
vertical axis (x=0 line), corresponding conditions are associated along the boundary
lines. Since both the piles along with the soft clay layer is associated with the bedrock,
the bottom boundary (y=0 line) was associated in both the directions. Resultantly, the
right hand side boundary (x=54 m) was associated in exclusively along the horizontal
direction which in turn went to provide for vertical displacements. The boundaries
were taken to be closed and therefore the pores of water contained within were only
allowed to evaporate from the top of the soft clay which was possible after calibrating
the pore water pressure to be zero at the border of the coarse grained fill and the soft
clay layer (y= 10m line).
The conclusions derived from the two-dimensional numerical modelling are herewith
This section makes a comparison of all the four situations already discussed with
respect to the case studies presumed for this section, using aspects of the settlement,
lateral displacement of the embankments and pile, vertical stress distribution with
respect to piles and the foundation soil., forces and bending in piles.
The lateral movement observed at the embankment toe and piles are considered in all
the four situations. Therefore, Figure 67 is representative of the lateral deformation in
the embankment in comparison to time. The case 1 is compared with ABAQUS case
study (Ariyarathne) and the results were reasonably same. Thereafter case 1 was compared
with the remaining case.
40 Case 1
Case 2
30 Case 3 (1:40)
Case 3 (1:20)
Case 3 (1:13)
10 Case 4 (1:40)
Case Study - UWS
0 200 400 600 800 1000 1200 1400 1600
The highest lateral displacement was observed in case 2, Case 3 (1:40) was observed
to have higher lateral displacement than case 1. However by increasing the slope of
the pile, Case 3 -1:20 and 1:13 were observed to have less lateral displacement than
case 1 which implies that inclined piles at batter slope can reduce the lateral
displacement compared to than geosynthetic reinforcement. On the other hand it was
noted that case 4 (1:40) was observed to have less lateral displacement than all the
other case but bit higher comparing with Case 3 (1:13).
Case 1
Case 2
20 Case 3 (1:40)
Case 3 (1:20)
Case 3 (1:13)
0 10 20 30 40 50 Case 4 (1:40)
This section evaluates the vertical stress distribution within the piles and the soil in the
foundation. Figure 69 reflects how vertical stress is spread out on the surface of the
ground comprising the coarse grained fill layers and the surfaces of the piles. The stress
lines are made at the tail end of the 4 year consolidation period, and the horizontal axis
is taken to be the distance from the embankment's centre till the toe. As per Figure 69,
In all case, foundation soil stress is brought down while conversely the stress on the
piles exhibits significantly higher values which can be credited to soil arching in the
embankment fill in consideration of differences between the soil in the foundation, and
the piles. A greater quantum of the embankment load is transmitted to the piles in
consideration of soil arching once piles are added to the system as per the vertical
stress distribution.
Vertical Stress (kN/m^2)
400 Case 2
0 5 10 15 20
Distance from the Center (m)
Figure 68: Vertical stress on the ground surface at the base of the embankment
Changes in the vertical stress levels on the soil in the foundation in all cases shows
increasing values throughout the construction phase, but then gradually comes down
during the subsequent consolidation period. Correspondingly, and inversely the
vertical stress measures on the piles gradually increases during the construction period
and continues so till it stabilizes during the consolidation period. Therefore, this goes
on to exhibit that a stress transfer is going on relative to the foundation soil to the piles
during the period of the consolidation which is attributed to soil arching. The
Case 2
Case 3 1:40
Case 3 1:20
Case 1:13
Case 4 1:40
0 5 10 15 20
Distance from the Center (m)
Case 3 1:40
Case 4 1:40
0 5 10 15 20
Distance from the Center (m)
The above two graphs are extraction of figure 69, Case 4 (1:40) implies that using inclined
piles at the batter slop can generate more stress at the top of piles below batter slope which is
better than Case 1.
7.3.3 Settlements
The distribution of the settlement adjacent to the top of the surface under the
embankment base, at the end of the consolidation is represented in Figure 70.
Corresponding downward positions are shown on the negative vertical axis. As per the
representation, settlements are reflected significantly when either piles or geo-
synthetic reinforcements are not observant, which is subsequently brought down on
introducing piles. Later, adjustments made for piles are observed to be insignificant in
comparison to the settlements observed for foundation soil. Therefore, on transferring
significant measures of embankment loads onto the piles with the help of soil arching,
stress levels on the soil at the foundation is observed to decrease with the same also
reflected in the settlement. Adding in a geo-synthetic layer results in the foundation
soil stress to be brought down as reflected in case 1. Figure 70 reflects that settlement
increases corresponding to the addition of a geo-synthetic layer is minimal at the centre
and at the toe of the embankment and less settlement below the batter slope when
inclined piles were used (case 3). Nevertheless, settlement characteristics hugely
improve in-between the centre and the toe since the sidewise movements related to the
embankment goes down appreciably after the addition of a geo-synthetic layer. The
follow-up downward shifts due to uniform load distribution.
Case 1
Settlement (mm)
Case 2
-30 Case 3 (1:40)
Case 3 (1:20)
Case 3 1H 13V
Case 4 (1:40)
Distance from the Embankment Center (m)
Settlement (mm)
Case 1
Case 3 (1:40)
Case 4 (1:40)
Distance from the Embankment Center (m)
The above figure is an extract of figure 70, which incorporates only case 1, 3 & 4.
Typically the settlement along the ground surface in case 1 is much better than case 3.
However case 4 implies that by having both geosynthetic layer and inclined piles at
the batter slope can improve the settlement much better than case 1.
Settlement at Crest (mm)
-10 Case 1
Case 2
-15 Case 3 (1:40)
Case 3 (1:20)
-20 Case 3 (1:13)
Case 4 (1:40)
Distance from the Embankment Center (m)
Figure 71 shows the shape of the settlement at the top of the embankment
(embankment crest), considering that the differential settlement is less in case 1
comparing with case 2 and all case 3. Since the LTP in case 1 efficiently distribute the
load over the embankment, it validates that the differential settlement is low. Case 4
implies that the differential settlement can be reduced when using both geosythetic
reinforcement and inclined piles at batter slope.
Axial force, shear force, bending moment, lateral displacement and settlement of pile
were analysed. There weren't much different in axial force and settlement of piles
since they are fixed at the bottom of soft clay soil profile. (Standard Fixities)
60 Case2
50 Case 3 - 1:40
40 Case 3 - 1:20
30 Case 3 - 1:13
Case 4 - 1:40
0 5 10 15 20
Pile Distance (m)
In the usual design (case 1) the maximum shear force in the pile tends to increase from
left to right. When using inclined piles below the batter slope (case 3 and case 4), it
was observed that the shear force was reduced in the piles at 13.5 m and 16.5 m. When
increasing the slope it's also noticed that the shear force in 16.5 m pile was decreased
and then increased.
300 Case1
250 Case2
Case 3 - 1:40
Case 3 - 1:20
Case 3 - 1:13
Case 4 - 1:40
0 5 10 15 20
Pile Distance (m)
In the usual design (case 1) the maximum bending moment in the pile tends to increase
from left to right and reduced at the right end.When using inclined piles below the
batter slope (case 3 and case 4), it was observed that the bending moment in the pile
was reduced at 13.5 m and 16.5 m.
Maximum Lateral Displacment in Pile
Lateral Displacment (mm)
15 Case1
Case 3 -
5 1:40
Case 3 -
0 5 10 15 20
Pile Distance (m)
The above figure is a shade diagram of Case 1 showing the results of lateral
displacement. The highest lateral displacement is at the toe of the embankment and
below the batter slope, by changing the vertical piles below the the batter slope to
inclined piled (case 3 and case 4) proved that thecritical or maximum lateral
displacement can be reduced.
The above figure proves that in case 1, the vertical stress generated above the piles
which are at batter slope of embankment are less comparing to other piles, however
by changing those piles to inclined piles, the load that is transferred to soft clay below
can be reduced and transferred to pile.
It was also observed that by increasing the diameter of pile all the results such as lateral
displacement, settlement of the embankment system and axial force, shear force,
bending and total displacement in pile can be reduced and vertical stress on top of pile
can be increased. However increasing diameter of pile cannot be a cost effective
The cross engagements of GRPS embankments cannot be evaluated due to the absence
of any useful technique. The techniques, such as the unreinforced piled embankments
(old method) which were not addressed by other autors. We have obtained the
desirable findings for the above from the finite element program in which piles are
emphasized significantly along with inclined piles at the batter slopes. Without
applying the easy conventions, the GRPS system can be effectively modelled with the
help of finite element technique. Throughout, we can evaluate the pressures and shifts
in the system. On the other hand, the stiffness data and soil strength is essential for the
finite element analysis.
very reliable and equivalent results from the Terzaghi and Hewlett & Randolph
methods. But, the results from these methods are totally different from the outcomes
of PLAXIS. The influence of the soil resistance offered by the primary soil can be
analysed with the help of a finite element program. Due to the presence or absence of
supporting soil, we can observe the difference in the tensile strength of the geo-grid.
But, the width of the embankment and the tension in the support cannot be determined
through PLAXIS. So, more detailed investigation is needed in this domain.
With the help of advanced PLAXIS 2D, we can analyse the tensile stiffness and the
situation of the geo-grid on the pile top. But, it is a very hard task to create large plane
strain models in PLAXIS. The consistent values for the factors are delivered by plate
load tests, like the number of geo-grids, spacing between them and the width and
height of reinforced fill for the geotextile strengthening design. The lateral movement
of the piles can be evaluated through various techniques. Goh et. alhad suggested the
twisting moment in the pile on the basis of experiential associations. In early analysis,
this can be applied. But, a comprehensive investigation is required to be conducted.
The design results of the various empirical methods in the literature review have been
shown as inconsistent and in contradiction to the measured data as in Case study 6.2.
The guidelines are not strictly applied in the design practices. The design of the soil
arching needs to be worked on at first and then field measurements should be used for
verification. There is confusion in relevance to the design of geosynthetic tension.
There is an ambiguity related to the design of geosynthetic tension, that is whether it
should be designed as an equivalent to the total of the geosynthetic tension in the
presence of the soil arching calculation, or should it be taken as an equivalent to the
loads based on lateral earth pressure. In the other scenario, should it be taken as an
equivalent to the maximum of both the components. Measurements and numerical
studies need to be conducted for further verification of this aspect.
It also needs to be ascertained whether the use of several layers of geosynthetics will
be sufficient in practice and will it be beneficial for the practice. The inclusion of the
sub soil support in the design of the geosynthetics also needs to be debated through
research with specific relevance to the consolidation and creep settlements.
The short and long term settlements and horizontal deformations of piled
embankments are not addressed by the empirical methods. This proves as a drawback,
as the embankments on floating piles are specifically dependent on these aspects. The
embankments on floating are not supported by any sort of guidelines whatsoever.
Piled embankments have to suffer complicated issues in terms of interaction with the
soil. The uncertainties attached to these structures can be reduced to a greater extent
through numerical methods. Unfortunately, the design is not applied completely in the
practical scenario. A proper design process for modelling piled embankments needs to
be created through research and numerical analysis of piled embankments. It would be
better to base these calculations on a few but reliable assumptions in order to reduce
Calculation procedures can only be reduced through research, which is able to include
or verify the following aspects:
The ability of the numerical methods to include almost all the influencing factors in
the design of piled embankments has made it the centre of the research. The analytical
methods have not been given any attention due to their inability to consider all the
factors. Numerical analysis is also suffering from various uncertainties related to pile
embankments and there are no guidelines to direct them yet.
9 References
22. Kempfert, H.-G., Gobel, C., Alexiew, D. and Heitz, C. (2004). German
recommendations for reinforced embankments on pile-similar elements.
EuroGeo3 - Third European Geosynthetics Conference, Geotechnical
Engineering with Geosynthetics, pp. 279-284.
23. Kempton, G., Russell, D., Pierpoint, N. D., and Jones, C. J. F. P. (1998).
Two- and threedimensional numerical analysis of the performance of piled
embankment. Proceedings, 6th International Conference on Geosynthetics,
pp. 767-772.
24. Love, J., and Milligan, G. (2003). Design methods for basally reinforced
pile-supported embankments over soft ground. Ground Engineering, Vol.
36, No. 3, March, pp. 39-43.
25. McKelvey III, J. A. (1994). The anatomy of soil arching. Geotextiles and
Geomembranes, 13, 317-329.
26. McNulty, J. W. (1965). An Experimental study of arching in sand."
Technical Report No. I- 674, U.S. Army Engineer Waterways Experiment
Station, Corps of Engineers, Vicksburg, Mississippi, 170.
27. Miki, H. and Nozu, M. (2004). Design and Numerical Analysis of Road
Embankment with Low Improvement Ratio Deep Mixing Method, Geo-
Trans 2004, ASCE, No.126, Vol.2 ,pp.1395-1402.
28. National Highway Institute, August 2006, Ground Improvement Reference
Manual Volume II, USA.
29. Noughton, P. J., Kempton, G. T. (2005). Comparison of analytical and
numerical analysis design methods for piled embankment. Proc. of Geo-
Frontiers, Austin, USA.
30. Pleomteux, C. and Porbaha, A. (2004). CMC Foundation System for
Embankment Support - A Case History, Geo Support.
31. Poulos, H. G. (2007). Design Charts for Piles Supporting Embankments n
Soft Clay. Journal of Geotechnical and Geoenvironmental Engineering,
Vol. 133, No. 5, pp. 493-501.
32. Reid. W.M and Buchanan, N.W. (1984) "Bridge approach support piling."
Piling and ground treatment, Thomas Telford ltd, London.
10. Appendixes
10.1 PLAXIS 2D - Input models
Ca Ca Ca Ca Ca e
se se se 1H:4 se 1H:2 se 1H:1 Case 1H:40 stu
1 2 3 0V 3 0V 3 3V 4 V dy
Ti Ti Ti Ti Ti Ti
me Ux me Ux me Ux me Ux me Ux me Ux
[da [m [da [m [da [mm [da [mm [da [mm Time Ux [da [m
y] m] y] m] y] ] y] ] y] ] [day] [mm] y] m]
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 -3 0 0 0 0 0 0
0 1 0 1 0 -1 0 -2 0 -5 0 -1 0 1
0 1 0 1 0 0 0 0 0 -4 0 -1 0 1
0 3 0 3 0 1 0 2 0 -2 0 1 0 3
0 4 0 4 0 3 0 3 0 0 0 2 0 4
0 7 0 7 0 5 0 6 0 1 0 5 0 7
0 9 0 9 0 7 0 8 0 4 0 7 0 9
0 10 0 10 0 9 0 10 0 6 0 8 0 10
0 12 0 12 0 10 0 12 0 8 0 10 0 12
0 13 0 13 0 12 0 15 0 10 0 11 0 13
0 14 0 14 0 13 0 15 0 13 0 12 0 14
0 17 0 17 0 16 1 16 0 13 0 15 0 17
0 19 0 19 0 17 2 16 1 14 0 17 0 19
0 19 0 19 0 17 3 17 2 14 0 17 0 19
1 20 1 20 1 18 5 18 4 15 1 17 1 20
2 20 2 20 2 18 5 18 5 16 2 18 2 20
4 21 4 21 4 19 5 18 5 16 4 19 4 21
5 22 5 22 5 20 6 19 6 16 5 20 5 22
5 22 5 22 5 20 7 19 8 16 5 20 5 22
5 22 6 22 6 20 9 20 10 17 5 20 6 22
5 22 7 23 7 21 10 20 10 18 5 20 7 23
5 22 9 24 9 22 10 20 10 18 5 20 9 24
5 22 10 24 10 22 11 20 11 18 5 20 10 24
5 22 10 24 10 22 12 21 12 18 5 20 10 24
5 22 11 24 11 22 14 22 14 19 5 20 11 24
5 22 12 25 12 23 15 22 15 20 5 20 12 25
5 22 14 26 14 24 15 22 15 20 5 20 14 26
6 23 15 26 15 24 16 22 16 20 6 20 15 26
7 23 15 26 15 24 17 23 17 20 7 21 15 26
8 23 16 26 16 24 18 23 18 21 8 21 16 26
10 24 17 27 17 25 20 24 20 22 10 22 17 27
10 24 19 27 18 25 20 24 20 22 10 22 19 27
11 24 20 28 20 26 21 24 21 22 11 22 20 28
12 25 20 28 20 26 22 25 22 22 12 22 20 28
14 25 21 28 21 26 22 25 22 22 14 23 21 28
15 26 22 29 22 27 23 25 23 23 15 23 22 29
15 26 23 29 22 27 25 26 25 24 15 23 23 29
16 26 25 30 23 28 25 26 25 24 16 24 25 30
17 26 25 30 25 29 26 27 26 24 17 24 25 30
18 27 25 30 25 29 27 27 27 24 18 24 25 30
20 27 26 31 26 29 27 27 27 25 20 25 26 31
20 27 27 31 27 29 28 27 28 25 20 25 27 31
21 28 27 31 27 29 30 28 30 26 21 25 27 31
22 28 28 32 28 30 30 29 30 26 22 26 28 32
22 28 29 32 29 30 30 29 30 26 22 26 29 32
24 29 30 33 30 31 31 29 31 26 24 26 30 33
25 29 30 33 30 31 31 29 31 26 25 27 30 33
25 29 31 33 31 31 32 29 32 27 25 27 31 33
25 29 31 33 32 31 32 30 32 27 25 27 31 33
26 30 32 33 32 31 34 30 34 28 26 27 32 33
26 30 32 34 32 32 35 31 35 29 26 27 32 34
27 30 34 34 34 33 35 31 35 29 28 28 34 34
29 31 35 35 35 33 36 31 36 29 30 29 35 35
30 31 35 35 35 33 37 32 37 29 30 29 35 35
30 31 36 35 36 33 37 32 37 29 30 29 36 35
31 31 37 36 37 34 37 32 37 29 31 29 37 36
31 32 37 36 37 34 38 33 38 30 31 29 37 36
32 32 37 36 37 34 40 33 40 31 32 29 37 36
33 32 37 36 38 35 40 34 40 31 33 30 37 36
34 33 38 37 40 36 40 34 40 31 34 30 38 37
35 33 39 37 40 36 41 34 41 31 35 31 39 38
35 33 40 38 40 36 42 34 42 31 35 31 40 40
36 33 40 38 41 36 42 34 42 32 36 31 40 40
36 34 41 38 42 36 42 34 42 32 36 31 41 40
37 34 42 38 42 36 42 35 42 32 37 31 42 40
37 34 42 38 42 36 43 35 43 32 37 31 42 41
39 35 42 38 42 37 44 35 44 33 38 32 42 41
40 35 42 39 43 37 45 36 45 33 38 32 42 41
40 35 43 39 44 37 45 36 45 33 39 33 43 41
41 36 44 39 45 38 46 36 46 34 40 33 44 41
41 36 44 40 45 38 47 36 47 34 40 33 44 42
42 36 45 40 46 38 47 37 47 34 40 33 45 42
42 36 45 40 47 38 47 37 47 34 41 33 45 42
43 37 46 40 47 39 47 37 47 34 41 33 46 42
45 37 47 40 47 39 48 37 48 35 42 33 47 42
45 38 47 41 47 39 49 38 49 35 42 34 47 45
45 38 47 41 48 39 50 38 50 36 43 34 47 45
46 38 47 41 49 40 50 38 50 36 45 35 47 45
46 38 48 41 50 40 50 38 90 36 45 35 48 45
47 38 49 42 50 40 90 38 0 36 45 35 49 47
17 25
47 38 50 42 50 40 0 38 1 36 46 35 50 47
25 41 22
48 39 50 42 90 40 1 38 1 36 46 35 7 47
17 41 73 26
48 39 90 42 0 40 1 38 3 36 47 36 7 47
17 25 57 15 31
49 39 0 42 1 40 2 38 11 36 47 36 0 47
25 41 89 53
50 40 1 42 1 40 3 38 48 36 7 47
41 73 15 11
50 40 1 42 3 40 11 38 48 36 96 47
73 15 12
90 40 3 42 11 40 49 37 61 47
17 15 15
0 40 11 42 50 37 11 47
25 37.13
1 40 50 439
41 90.16 37.13
1 40 01 432
73 170.4 37.13
3 40 803 412
15 250.8 37.13
11 40 005 388
411.4 37.13
409 326
732.7 37.13
216 187
1511 842
Case 1
Case 2
20 Case 3 (1:40)
10 Case 3 (1:20)
0 Case 3 (1:13)
0 200 400 600 800 1000 1200 1400 1600
-10 Case 4 (1:40)
Case 1
Case 2
20 Case 3 (1:40)
10 Case 3 (1:20)
Case 3 (1:13)
0 10 20 30 40 50 Case 4 (1:40)
23.6 4.5 46.8 4.5 47.8 4.5 46.1 4.5 48.2 4.5 26.4
4.5 310 342 360 600 540 269 161 580 472 361 827
241 43 39 59 49 46 08 91 26 39 24 65
5.5 42.7 5.5 33.5 5.5 32.6 5.5 33.4 5.5 32.5 5.5 40.8
137 730 168 541 295 011 132 921 285 063 177 795
1 19 48 94 48 42 4 61 53 63 75 94
6.5 47.6 6.4 49.3 6.4 52.2 6.4 48.1 6.4 51.9 6.4 50.3
033 284 994 057 990 679 995 182 990 730 994 335
21 27 57 96 47 14 73 88 79 53 27 13
- - - - - -
7.4 27.3 7.4 19.2 7.4 17.6 7.4 19.9 7.4 18.4 7.4 23.2
929 342 820 522 685 448 859 078 696 470 810 441
32 46 65 25 46 69 06 29 05 32 78 43
7.4 979. 7.4 912. 7.4 883. 7.4 926. 7.4 885. 7.4 950.
929 993 820 666 685 423 859 100 696 303 810 761
32 21 65 51 46 47 06 89 05 13 78 35
7.5 978. 7.5 908. 7.5 875. 7.5 922. 7.5 878. 7.5 945.
076 073 195 225 343 353 153 576 331 040 206 630
81 75 65 06 14 68 76 22 58 16 42 08
- - - - - -
7.5 7.86 7.5 18.0 7.5 9.38 7.5 18.9 7.5 10.0 7.5 4.75
076 835 195 384 343 316 153 227 331 199 206 816
81 36 65 08 14 93 76 19 58 72 42 07
8.5 36.1 8.5 24.3 8.5 28.6 8.5 23.7 8.5 28.3 8.5 39.8
042 694 021 421 038 480 017 003 036 390 022 204
44 35 74 44 13 42 08 46 84 2 94 52
9.5 41.0 9.4 38.9 9.4 37.2 9.4 39.7 9.4 37.4 9.4 38.6
008 852 847 016 733 767 880 860 742 894 839 315
07 61 83 4 12 16 41 47 11 28 45 18
10. 27.4 10. 42.8 10. 44.2 10. 43.7 10. 43.8 10. 34.7
497 132 467 811 442 983 474 169 444 799 465 945
37 06 39 9 81 03 37 02 74 01 6 24
10. 565. 10. 539. 10. 510. 10. 551. 10. 512. 10. 528.
497 098 467 839 442 130 474 970 444 981 465 350
37 13 39 51 81 3 37 78 74 5 6 15
10. 567. 10. 580. 10. 578. 10. 584. 10. 579. 10. 557.
500 387 504 117 508 526 503 590 508 415 505 033
39 41 89 67 58 7 84 39 29 1 16 08
- - - - - -
10. 35.6 10. 23.5 10. 19.4 10. 23.6 10. 19.9 10. 28.9
500 118 504 811 508 334 503 866 508 869 505 173
39 49 89 1 58 98 84 2 29 37 16 77
- - - - - -
10. 35.7 10. 25.0 10. 22.4 10. 24.6 10. 22.4 10. 31.1
503 601 542 836 574 470 533 226 571 893 544 294
39 22 39 87 35 58 31 21 84 4 73 51
10. 87.4 10. 59.6 10. 61.7 10. 64.4 10. 64.3 10. 86.2
503 048 542 519 574 699 533 609 571 568 544 352
39 93 39 31 35 04 31 25 84 46 73 94
11. 47.8 35.7 11. 34.7 11. 34.1 11. 35.3 11. 40.2
270 649 11. 948 543 027 519 768 542 677 526 828
46 25 525 72 85 9 65 21 37 91 38 54
11. 39.0 12. 44.7 12. 50.2 12. 40.7 12. 50.6 12. 41.7
270 024 507 927 513 785 505 214 512 969 508 624
46 86 61 79 34 62 98 96 9 05 03 66
12. 40.8 13. 9.35 13. 10.2 13. 9.51 13. 10.2 13. 10.3
382 247 490 560 482 854 492 850 483 085 489 880
2 13 22 35 84 65 31 88 42 78 68 9
13. 34.6 13. 425. 13. 420. 13. 427. 13. 422. 13. 440.
493 640 490 430 482 592 492 011 483 929 489 536
95 64 22 58 84 02 31 37 42 13 68 58
13. 30.5 13. 399. 13. 375. 13. 405. 13. 378. 13. 412.
493 191 527 365 548 637 521 406 546 514 529 319
95 76 72 61 61 02 78 79 97 1 24 7
30.3 13. 20.9 13. 23.9 13. 19.0 13. 22.2 13. 19.1
13. 888 527 777 548 685 521 869 546 642 529 507
5 55 72 55 61 17 78 33 97 44 24 23
14. 35.6 14. 29.1 14. 26.6 14. 28.8 14. 14. 27.3
495 609 510 038 518 402 508 762 517 26.6 510 476
27 98 33 3 11 63 12 13 5 563 89 58
15. 28.0 15. 36.4 15. 32.9 15. 34.4 15. 31.9 15. 36.5
490 909 492 581 487 889 494 158 488 845 492 745
54 18 94 92 61 69 45 52 03 72 55 04
16. 26.2 16. 4.98 16. 5.92 16. 6.71 16. 7.25 16. 5.45
485 761 475 323 457 451 480 439 458 121 474 974
81 46 54 34 11 97 78 49 55 47 2 26
16. 29.8 16. 93.6 16. 88.5 16. 92.4 16. 89.3 16. 109.
485 186 475 053 457 486 480 711 458 211 474 343
81 42 54 96 11 62 78 73 55 05 2 89
29.8 16. 96.4 16. 93.8 16. 95.0 16. 94.4 16. 112.
16. 906 513 751 522 336 510 041 522 273 513 249
5 48 04 68 88 23 25 3 11 58 76 94
16. 7.51 16. 14.3 16. 16.3 16. 14.8 16. 16.2 16. 4.95
509 405 513 902 522 869 510 983 522 718 513 602
47 24 04 74 88 51 25 49 11 34 76 89
16. 13.6 17. 16.9 17. 16.5 17. 16.4 17. 15.5 17. 17.2
509 496 986 475 977 769 989 988 977 041 986 130
47 73 96 72 12 38 75 15 9 15 24 36
Vertical Stress on the ground surface on the ground surface at the base
of the embankment
Vertical stresss (kN/m62)
600 Case 2
Case 3 1:40
400 Case 3 1:20
Case 1:13
Case 4 1:40
0 5 10 15 20
Distance from the centre of the embankment (m)
Vertical Stress (kN/m^2)
Case 2
Case 3 1:40
Case 3 1:20
Case 1:13
Case 4 1:40
0 5 10 15 20
Distance from the Center (m)
- - - - -
7.411 10.9 10.44 8.33 6.503 48.6 6.499 48.5 6.499 48.1
765 588 863 566 351 532 047 427 159 164
- - - - -
0.63 10.44 8.33 7.488 1.43 7.468 2.78 7.472 2.52
7.5 404 863 566 039 315 546 797 253 413
- - - - -
0.63 10.50 1.82 7.488 1.43 7.468 2.78 7.472 2.52
7.5 404 771 338 039 315 546 797 253 413
- - - - -
8.470 46.8 10.50 1.82 7.512 1.63 7.534 3.28 7.530 2.91
588 131 771 338 994 956 314 511 269 954
- - - - -
9.441 51.8 10.56 7.92 7.512 1.63 7.534 3.28 7.530 2.91
177 799 678 231 994 956 314 511 269 954
- - - - -
10.41 12.2 10.56 7.92 8.505 45.9 8.503 45.3 8.503 44.5
177 638 678 231 007 005 813 437 363 113
- - - - -
10.41 12.2 11.53 38.8 9.497 49.1 9.473 48.2 9.476 47.0
177 638 938 437 019 233 312 162 457 807
- - - - -
0.56 12.51 34.2 10.48 2.27 10.44 8.80 10.44 7.68
10.5 701 199 054 903 648 281 39 955 565
- - - - -
0.56 13.48 1.16 10.48 2.27 10.44 8.80 10.44 7.68
10.5 701 459 323 903 648 281 39 955 565
- - - - -
11.47 39.3 13.48 1.16 10.50 0.83 10.50 1.89 10.50 1.69
059 259 459 323 164 344 858 176 757 827
- - - - -
12.44 33.9 13.54 3.05 10.50 0.83 10.50 1.89 10.50 1.69
118 536 366 753 164 344 858 176 757 827
- - - - -
13.41 7.42 13.54 3.05 10.51 2.18 10.57 8.26 10.56 7.17
177 008 366 753 414 322 435 638 558 4
- - - - -
13.41 7.42 14.51 20.8 10.51 2.18 10.57 8.26 10.56 7.17
177 008 627 108 414 322 435 638 558 4
- - - - -
0.53 15.48 15.3 11.50 38.0 11.54 36.9 11.53 35.8
13.5 144 887 15 941 892 385 904 868 611
- - - - -
0.53 16.46 1.49 12.50 33.5 12.51 32.4 12.51 31.2
13.5 144 147 438 468 77 334 851 177 61
- - - - -
14.47 21.4 16.46 1.49 13.49 0.29 13.48 0.88 13.48 0.82
059 815 147 438 995 903 284 857 487 158
- - - - -
15.44 16.2 16.52 0.66 13.50 0.30 13.48 0.88 13.48 0.82
118 36 055 422 013 527 284 857 487 158
- - - - -
16.41 2.76 16.52 0.66 13.54 2.63 13.54 3.00 13.54 2.67
177 066 055 422 33 021 861 796 288 234
- - - - -
16.41 2.76 17.97 8.48 13.54 2.63 13.54 3.00 13.54 2.67
177 066 945 078 33 021 861 796 288 234
- - - -
0.44 14.52 20.7 14.51 20.5 14.51 20.1
16.5 104 604 917 811 534 598 607
- - - -
0.44 15.50 15.2 15.48 15.2 15.48 14.9
16.5 104 879 129 761 089 907 329
- - - -
16.55 1.00 16.49 0.39 16.45 1.20 16.46 1.03
861 57 153 011 711 344 216 343
- - - -
16.55 1.00 16.49 0.39 16.45 1.20 16.46 1.03
861 57 153 011 711 344 216 343
- - - -
18.01 7.42 0.15 16.52 0.27 16.52 0.23
45 231 16.5 191 288 549 018 909
- - - -
18.01 7.42 0.15 16.52 0.27 16.52 0.23
45 231 16.5 191 288 549 018 909
- - - -
18.07 7.45 16.50 0.22 17.97 8.39 17.97 8.42
66 665 565 113 712 489 982 183
16.50 0.22
565 113
18.00 8.46
211 235
18.00 8.46
211 235
18.01 8.46
114 995
18.01 8.46
114 995
Settlment (mm)
Case 1
Case 2
Case 3 (1:40)
Case 3 (1:20)
Case 3 1H 13V
Distance from the centre of the embankment (m)
-20 Case 1
Settlement (mm)
Case 2
-30 Case 3 (1:40)
Case 3 (1:20)
Case 3 1H 13V
Case 4 (1:40)
Distance from the Embankment Center (m)
- - -
- - 7.01 25. 15. 13. -
15. 16. 072 185 344 780 15.
10.5 431 10.5 274 7 3 10.5 5 10.5 8 10.5 226
7.01 25.
072 185
7 3
8.14 396
198 5
9.27 20.
323 429
3 8
10.4 16.
044 486
9 7
10.4 16.
044 486
9 7
10.5 16.
241 020
5 9
Settlement at Crest (mm)
-10 Case 1
Case 2
-15 Case 3 (1:40)
Case 3 (1:20)
Distance from the Embankment Center (m)
x Axial Axial
piles distance Axial kN/m Axial kN/m Axial kN/m kN/m Axial kN/m kN/m
60 Case1
50 Case2
40 Case 3 - 1:40
30 Case 3 - 1:20
20 Case 3 - 1:13
10 Case 4 - 1:40
0 5 10 15 20
Pile Distance (m)
300 Case1
250 Case2
200 Case 3 - 1:40
Case 3 - 1:20
50 Case 3 - 1:13
0 Case 4 - 1:40
0 5 10 15 20
Pile Distance (m)
12 Case1
8 Case2
6 Case 3 - 1:40
2 Case 3 - 1:20
0 Case 3 - 1:13
-2 0 5 10 15 20
-4 Case 4 - 1:40
Pile Distance (m)