Abstract:

Through different consolidation and shearing paths, unloading shear strength tests were carried out on typical Guangzhou soft soil. Different shear strengths were obtained through different test methods. The unloading shear strength parameters were lower than loading shear strength parameters. For foundation pit engineering, the DCU (lateral unloading triaxial test) is suitable for the actual situation. Nevertheless owing to its difficulty, the DGK (preloading consolidation, followed by unloading to different consolidation pressures, and quick shear test in subsequence) can be employed instead. The test also showed that the stress-strain curve with work hardening was still hyperbola under unloading condition. Unloading shear strength was smaller than loading shear strength when given the same confining pressure. Initial tangential unloading modulus was smaller than initial tangential loading modulus, therefore, when the loading modulus is used instead of the unloading modulus, the project is prone to be in hazard. 

Key words:  soft soil, unloading strength, unloading modulus