Strength and deformation characteristics of silty clay under frozen and unfrozen states

Abstract

Frost damage of soil foundations of engineering structures is controlled by mechanical properties of soil under frozen and unfrozen states, existing widely in cold regions such as Genhe area that is termed as the “pole of cold” in China. For investigating engineering properties of soil in cold regions, a series of triaxial compressive tests were carried out on both frozen and unfrozen Genhe silty clay with different degrees of compaction under different confining pressures. The test results show that the stress-strain curves gradually change from softening to hardening with increasing confining pressure, temperature and decreasing compaction degree. Additionally, both axial and radial deformation is more sensitive to lower confining pressures. An accurate method was proposed for determining the elastic modulus. The elastic modulus and strength decrease significantly as the state of soil changes from frozen to unfrozen. The effect of compaction degree on radial deformation, strength and failure strain is gradually eliminated with the increase of confining pressure, which can be observed in both frozen and unfrozen soil. The isotropic tensile strength and the cohesion were obtained in the stress spaces of p-q and σ-τ respectively, and the ice cementing force was identified by adopting the difference of the two strength parameters between frozen state and unfrozen state. The results indicate that the ice cementing force calculated by two strength parameters is consistent, which increases with increasing compaction degree.