Researches on mechanical properties of soil under conditions of excavation unloading in Guangzhou

Abstract

Abstract. Based on the investigation of the distribution of strata in the downtown area of Guangzhou City, simulating the stress path of excavating foundation, the triaxial pressure tests on isotropic consolidation and K0 consolidation conditions, the lateral unloading tests and the axial unloading tests on mucky soil and silty clay were performed by using SLB-1 stress-strain controlled triaxial shear penetration apparatus, in order to research the loading and unloading deformation properties of foundation soil, and change rules with strain and strength properties of pore water pressure under different stress paths. The results show that there exist different characters of stress-strain curves of the soil under different stress paths, mucky soil and silty clay are different in mechanical properties, while the stress-strain curves of them present obvious nonlinear type; the failure model of soil under normal triaxial compression conditions, K0 compression conditions and lateral unloading conditions presents compression-shear type, and under the axial unloading conditions presents longitudinal stretch type; change rules of stress-strain curves of the soil are influenced by average consolidation stress, plastic index and confining pressures; change rules of pore water pressure are also influenced by average consolidation stress, stress path and properties of the soil, which can be fit by exponential decay function; stress-strain curves of pore water under K0 compression-axial unloading conditions can be fit by quadratic parabolic equation.