A comprehensive study on soil consolidation

Abstract

In this research, soil consolidation is explored in a comprehensive analytical and experimental study. The pore pressure development and dissipation for clay at its liquid limit under one-dimensional compression was investigated using the mid-plane pore pressure measurements. In general, the Terzaghi’s theory of consolidation predicted the pore pressure dissipation and the percent consolidation accurately as long as the sample was in a normally loaded state. For a preconsolidated state however, the results obtained by Terzaghi theory are doubtful. Coefficient of consolidation for smaller pressures varied during consolidation, and although the soil was in a fully saturated state for relatively high pressure increments, the pore pressure developed was less than the applied pressure. Then, the effect of different pressure increment ratios on one dimensional consolidation tests has been studied. The secondary compression effects have been founded to increase as the pressure increment ratio is reduced. Consolidation of a clay layer delimited between sheets with small permeability was also investigated in this study. The consolidation theory of compressible soils usually assumes drainage-free boundaries. This change in boundary conditions at the drainage surface necessitates the use of an approximate technique for solution of the governing partial differential equation. In this study, the solution was obtained by using the Galerkin Method and compared with the “free drainage” case. As expected, the consolidation in the case of restricted drainage proceeds at a much lower rate. The compression consolidation behavior of trampled clays in a semi- saturated state was also analyzed in this research program. It is generally known that the type and energy of compaction bring about deviations in the soil structure and hence, in its engineering properties. Therefore, in the experimental phase of this study, soils were prepared by different trampling efforts and also by different compaction methods. Finally, a reasonably realistic theory of soil consolidation has been proposed and the effect of variable permeability and compressibility on the consolidation behavior was investigated followed by a mathematical treatment of the behavior. Subsequently, laboratory consolidation tests with mid-plane pore pressure measurements were conducted on different kinds of clay.