ABSTRACT

This chapter presents the definition and physical meaning of effective stress based on the equilibrium differential equation of soils. It indicates that effective stress is the soil skeleton stress induced by the external forces, excluding pore fluid pressure. The chapter discusses the correlation between effective stress and shear strength for unsaturated soils. It shows primary verification of the effective stress on the determination of deformation on unsaturated soils. The chapter presents the simple application of effective stress on the stress calculation for the soil layers. The constitutive relationship of soils plays a key role in soil mechanics, especially in characterizing the stress and strain relationship of a soil. The pore fluid pressure is applied on the surfaces of soil particles. It only results in the volumetric deformation of soil particles and affects the shear strength on the interfaces of soil particles. The shear strength of a soil is that of the soil skeleton, which is determined by skeleton stress.