The effect of saturation and shrinkage deformation on the small strain stiffness of soils

The small strain stiffness and Poisson's ratio of soils, closely related to the degree of saturation of the soil, play a key role on predicting the structure deformation caused by the interaction between soil and structure on the shallow surface. Adopting the experimental instrumentation developed independently, experimental investigations on soil cakes were conducted to explore the dependencies of the small strain stiffness and Poisson's ratio of fine-grained soils on the evolution of degree of saturation which is induced by adjusting environmental humidity under zero external load. The experimental results show that evolution of both the elastic wave velocity and small strain stiffness of fine-grained soils with the degree of saturation can be identified three characteristic stages including boundary effect stage, transition stage and residual stage. With decreasing the degree of saturation, the compression wave velocity and bulk modulus first decrease and then increase, the shear wave velocity and shear modulus increase, while the Poisson's ratio of the clay decreases linearly. In contrast, the Poisson's ratio of the silty clay changes limitedly and keeps in the value of 0.37 when the degree of saturation is lower than 85%. It is shown that the degree of saturation plays a more important role on the change of the small strain stiffness and Poisson's ratio of clay than on that of silts. © 2020, Science Press. All right reserved.