Abstract: The understanding of engineering properties of unloading soil is the key to solving the problems in excavation of foundation pits. Gongbei tunnel in Zhuhai of Hongkong-Zhuhai-Macau Bridge is located in marine facies soft clay. The excavation depth and width of its foundation pit are both very large. The researches on of constitutive model and model parameters of the foundation pit soil under unloading stress path are of great significance to the engineering design. The marine faces sediment-mucky soil and plastic silty clay are are studied so as to determine their K0 coefficients. K0 drained consolidation expririments are performed under the confining pressures of 100, 200, 400 and 600 kPa by using the stress controlled triaxial apparatus. Unloading tests with various stress paths are conducted after the soil samples are completely consolidated. According to the non-linear feature of stress-strain relationship curve, the Duncan-Zhang E-μ model is adopted as the constitutive model for soil. According to the experimental results, 8 basic parameters are determined, and this study provides important basis for the FEM analysis of the foundation pit. |