Parameter back-analysis of hardening soil model for granite residual soil and its engineering applications

In recent years, construction works near the operating metro tunnel in granite residual soil have been gradually increasing, and the impact of these construction works on the safety of shield tunnel should not be ignored. Finite element method is an effective method to evaluate the influence of adjacent construction on shield tunnel, but its reliability highly depends on the reasonable selection of soil constitutive model and parameters. In this paper, the current situation of parameter selection of hardening soil model for granite residual soil is firstly reviewed. Then a back-analysis method for determining the parameters of granite residual soil based on the self-boring pressuremeter test (SBPMT) is proposed. Finally, the obtained back-analysis parameters are applied to the engineering case of foundation pit excavated overpass existing shield tunnel for method verification, and more reasonable values of parameters of hardening soil model for granite residual soil are determined. The results show that the strength parameters of hardening soil model for granite residual soil can be determined by laboratory tests, and the stiffness parameters of E₅₀^ref, E_oed^ref and E_ur^ref are the key parameters for the back-analysis. The ratio of E₅₀^ref: E_oed^ref: E_ur^ref from 1:1:3 to 1:1:5 is suitable for engineering practice, and the value of E₅₀^ref ranges from 36 MPa to 43 MPa according to different ratios.