undergo consolidation settlement not only the action action of external loads (surcharge loads) but also under its own weight or weight of soils that exist above the clay. Clays also undergo settlement when dewatered (groundwater pumping) because the effective stress on the clay increases. Coarse-grained soils do not undergo consolidation settlement due to relativity high hydraulic conductivity compared to clays. Instead, Coarse-grained soils undergo the immediate settlement. History and terminology The first modern theoretical models for soil consolidation were proposed in the 1920s by Terzaghi and Fillunger, according to two substantially different approaches. The former was based on diffusion equations in eulerian notation, whereas the latter considered the local Newton’s law for both liquid and solid phases, in which main variables, such as partial pressure, porosity, local velocity etc., were involved by means of the mixture theory. Terzaghi had an engineering approach to the problem of soil consolidation and provided simplified models that are still widely used in engineering practice today, whereas, on the other hand, Fillunger had a rigorous approach to the above problems and provided rigorous mathematical models that paid particular attention to the methods of local averaging of the involved variables. Fillunger’s model was very abstract and involved variables that were difficult to detect experimentally, and, therefore, it was not applicable to the study of real cases by engineers and/or designers. Nevertheless, this provided the basis for advanced theoretical studies of particularly complex problems. Due to the different approach to the problem of consolidation by the two scientists, a bitter scientific dispute arose between them, and this unfortunately led to a tragic ending in 1937. After Fillunger’s suicide, his theoretical results were forgotten for decades, whereas the methods proposed by Terzaghi found widespread diffusion among scientists and professionals. In the following decades Biot fully developed the three-dimensional soil consolidation theory, extending the one-dimensional model previously proposed by Terzaghi to more general hypotheses and introducing the set of basic equations of poroelasticity. Today, the Terzaghis’ one dimensional model is still the most utilized by engineers for its conceptual simplicity and because it is based on experimental data, such as oedometer tests, which are relatively simple, reliable and inexpensive and for which theoretical solutions in closed form are well known. According to the "father of soil mechanics", Karl von Terzaghi, consolidation is "any process which involves a decrease in water content of saturated soil without replacement of water by