Stress Distribution and Settlement in Soils

This chapter describes the stress distribution and the calculation of settlement within an idealized elastic soil mass due to applied external and internal loading. The elastic properties include the Modulus of Elasticity E s and Poisson 1 s ratio μ. For soils where the compressibility characteristics are non-uniform and depend upon the state of the stress (e.g. sands), the concept of a compressibility index m v is introduced. The coefficient of (volume) compressibility is defined as the ratio of the strain increment to the stress increment in a specified direction caused by external or internal loading. The soil is assumed to be an ideal semi-infinite homogenous elastic material obeying Hooke’s law, and the elastic stress-strain model shown in Figure 4.4(a) is employed to determine the stress distribution within the soil. Furthermore, the soil is assumed to be weightless which means the stress field resulting from the solution of the equilibrium and compatibility conditions satisfies only the boundary conditions. Nevertheless, with a known stress field the strains, and consequently the deformation of the soil layer and surface settlement, can be evaluated.