It is experimentally found that shut-in pressure conforms with the fracture initiation pressure if fracture surfaces are uniformly loaded by fluid. The article shows that equaling minimal stress and shut-in pressure in local fractures results in overestimates. The error depends on the length of a hydrofracturing facility and is high under low compression in rocks (5-10 MPa). The authors put forward decisions aimed at improvement of accuracy and enhancement of information content of hydraulic fracturing in the in situ stress measurement.
The authors describe operation of a laser deformograph within the integrated geodynamic monitoring system in Streltsov Ore Field. Capabilities and design features of the deformograph are discussed. The article demonstrates feasibility of highly accurate measurements of deformation field parameters in an operating mine. Specificity of natural oscillations of the Earth is defined, and deformation of rock mass depending on energy of a destruction source is evaluated.
Considering features of wave pre-destruction (microfailure) of rocks under blasting, the authors put forward a new investigation approach with the use of relations of dynamic elastic stress distribution in rocks and theory of cracks. The obtained relation to estimate pre-destruction zone size in relatively solid rocks under confined explosion involves pressure of gases in explosion chamber, rock pressure, crack resistance of rocks, characteristic dimension of natural jointing (presence of defects) and deformation characteristics of rocks. It is shown that dimension of pre-destruction zone in rocks depends both on natural and production factors and can differ by a few times.
The factors that have significant influence on efficiency of rotary-percussion rock drilling with downhole machines are discussed. The results obtained in physical simulation of dynamic driving of rock-breaking indenters in rocks are reported. The results are analyzed from the standpoint of the phenomenon of alternating response of rocks to dynamic impacts.
The article presents a procedure to calculate hydraulic pressure losses in hole drilling with units equipped with replaceable core receivers and using non-Newtonian mud fluids. It is found that main hydraulic loss takes place when mud fluid flows in clearing between a drill string and drill hole walls. Numerical modeling has shown that it is possible to reduce hydraulic pressure loss by 76.5-89.0% by increasing drill string diameter by 2 mm. Based on the analytical research results, diamond drill bits and underreamers with the outer diameters of 78.0 and 78.4 mm, respectively, are manufactured for drilling operations in Talnakh ore field.
Authors review key approaches to designing small-size air drill hammers. The approach to increasing impact capacity of air drill hammers by means of buildup of blow frequency is substantiated. The experimentally obtained and compared characteristics of air drill hammers equipped with the heads made of steel and titanium prove feasibility of increasing impact capacity by means of using low density materials. The technology of thermal treatment of a titanium-alloy hammer head is described, and its laboratory testing results are reported.
The analysis of methods to account for stripping time difference at the stage of determination of limits in deep open pit mining reveals advantages and shortcomings of the methods and provides a principled approach to determination of a discount ultimate stripping ratio for the most representative geological and geotechnical conditions of diamond-bearing ore bodies in the form of single pipes. Discounting of ultimate stripping ratios is based on adding the common formula with an average mean discount coefficient represented by a correlation of mining rate decrease, stripping zone height and highwall slope angle. It is shown that target variation of the factors included in the discount ultimate stripping ratio allows considerable influence on depth and efficiency of open pit mining.
The article describes the applied research findings on selecting a resource-saving technology to ensure drastic reduction in loss of high-grade Kyshtym quartz. The economical-mathematical modeling yields relationships between mine efficiency, ground conditions, mine design and technology factors, and the optimal variant of a combination mining technology is determined using the maximum profit criterion. Full-scale physical simulation of closed-spaced charge blasting effect on reduction in overgrinding of quartz is discussed. Drilling and blasting pattern for experimental breaking of quartz by explosions is determined.
Using Hammett indicators, X-ray fluorescence spectroscopy and atomic force microscopy, the authors analyze influence of high-voltage nanosecond impulses on structure and chemistry of surface and on process properties of calcium-bearing minerals. As a result of impulse energy inputs for t ≤ 30 s, the change in the structure and functions of mineral surface includes: enhancement of electron-donor capacity and formation of structural defects on the surface of fluorite, and enhancement of acceptor capacity of the surface of calcite and scheelite. Pre-treatment of mono-mineral samples by electrical impulses increases flotation ability of calcium-bearing minerals: increment in froth recovery makes 10–12% for scheelite, 5–6% for fluorite and 7–8% for calcite.
New information is obtained on composition and properties of a bio-reagent-oxidizer generated by mesophilic aerobic chemo-tropholytic bacteria Acidithiobaccilus ferrooxidans under oxidation of iron ions (II) in sulfuric acid solution. The composition and properties of the bio-reagent are compared with iron sulfate (III) used to intensify agitation and heap leaching of metals from sulfide ores and concentrates. The research with IR spectroscopy, mass spectrometry, Moessbauer spectrometry and potentiometry has revealed distinctive features of the bio-reagent and explained the experimentally observed increase in its oxidative activity when interacting with mine.
The article presents data of experimental studies into magnetic properties of iron-bearing sulfide and nonsulfide minerals under radiation and heating. It is found that bulk magnetic susceptibility has increased more than 100 times in pyrite and by 6 times in bauxite ore. Usefulness of radiation-and-heating magnetization in modification and processing of bauxite and tin-bearing minerals is demonstrated.
The discussed challenge and its prospects in mining geoinformation science are connected with Big Data concept-flows of large sets of various data on mining. The authors describe Big Data technology and its general implementation on mini-clusters using Hadoop and MapReduce with case studies presented.