Stress-deformation characteristics of silty soil based on K₀ consolidation and drainage unloading stress path tests

Based on different initial stress states and unloading stress ratios, the unloading stress path drainage tests under K₀ consolidation are carried out on the silty clay sampled from the construction site of the South-to-North Water Diversion Project. The specimens are firstly consolidated with a given value of K₀ under different confining pressures. Then, to simulate the stress path at different locations of excavation soil, the stress decrements are applied from both the axial and the radial directions with different stress ratios. The test results show that the stress-strain behavior of soil is closely related to the stress path. Under different unloading stress ratios, the specimen may be compressed, elongated firstly and then compressed or elongated. The critical value of unloading stress ratio determining compression and extension is determined by the initial consolidation state and soil properties. With the decrement of the unloading stress ratio, the value of volume dilation increases. The tests also verify that the loading mode and stress path have little effect on the strength parameters. The characteristics observed from the tests are significantly different from those of the conventional triaxial test results. It is necessary to develop a proper constitutive model, which can describe the unloading stress path of the soil, and to carry out the stress and deformation analysis of the excavation soil.