Abstract:

Through direct shear and consolidation tests, the variation laws of cohesion c, internal friction angle φ, and compressibility index of granite residual soil (GRS) under drying-wetting cycles (DWC) and construction vibrations, as well as the parameter prediction formulas, are rationally obtained, which are then applied to the refined numerical simulation of deep excavation of a subway station. The experimental results indicate that c exhibits a nonlinear decay with the increase of the number of DWC and the vibration time, φ shows a fluctuating upward tendency with the increase of the number of DWC, and the effect of vibration on φ decreases as the number of DWC increases. The compression coefficient a_v1-2 increases linearly with the number of DWC without vibration and fluctuates after the vibration. The reference tangent modulus decreases slowly with the increase of number of DWC without vibration, but decreases sharply, then slowly, and finally increases after the vibration. By considering the effects of DWC and construction vibration, the foundation pit is divided into 6 impact zones, and the model parameters are selected from the deteriorated soil parameters corresponding to each impact zone. It is shown that the refined finite element simulation results agree well with the field monitoring values of the surface settlement and the horizontal displacement of diaphragm wall, which can provide a practical guidance for the design and construction of the residual soil foundation pit.

Key words: residual soil, drying-wetting cycle, vibration, strength and deformation property, numerical simulation