Theory of Consolidation

Abstract

Soft soils such as sand and clay consist of small particles, and often the pore space between the particles is filled with water. In mechanics this is denoted as a saturated porous medium. The deformation of such a material depends upon the stiffness of the porous material, but also upon the behaviour of the fluid in the pores. In particular, the flow of the pore fluid influences the deformation of the soil. If the permeability of the material is small, the deformations may be considerably hindered, and retarded, by the pore fluid, which needs considerable time to be expelled from the soil. The simultaneous deformation of the porous material and flow of pore fluid is the subject of the theory of consolidation. In this chapter the basic equations of this theory are derived, for the case of a linear material. The theory was developed originally by Terzaghi (1925) for the one-dimensional case, and extended to three dimensions by Biot (1941), and it has been studied extensively since. A simplified version of the theory, in which the soil deformation is assumed to be strictly vertical, is also presented in this chapter. The analytical solutions for two simple examples are given. In chapters 16 and 17 the numerical solution of consolidation problems is considered.