Tests on mechanical behavior of unsaturated decomposed granite and its modelling considering finite deformation

Abstract Generally speaking, most of the geomaterials in the surface ground are in an unsaturated state. The mechanical and hydraulic properties of unsaturated soil are much more complicated than those of saturated soil. To rationally describe these properties, it is important to couple the stress-strain relation of the unsaturated soil with its water retention characteristics using rational state variables. In this paper, oedometer and triaxial compression tests on decomposed granite under constant-suction and constant degree of saturation conditions were conducted. Based on the test results, a modified constitutive model was proposed to build an incremental relation between the degree of saturation and suction that considers the influence of finite deformation. The modified model was utilized to simulate the corresponding laboratory tests. It is found that the modified constitutive model has satisfactory accuracy to describe the mechanical and hydraulic properties of unsaturated decomposed granite, which verified the reasonability of the assumption adopted in this paper. The test results are also helpful for the understanding of the moisture characteristics of the decomposed granite under constant degree of saturation condition.