Numerical simulation of excavation effects on tunneling with IGS small strain model

The excavation will produce additional loads on the adjacent tunnel, causing tunnel deformation. For the numerical simulation of this problem, the constitutive model for soils is very important. The hardening soil small (HSS) model has been widely used for the simulation of excavation in soft soils. For too many parameters of HSS model resulting in complexity for engineering application, a nonlinear elastic model—IGS (intergranular-strain) model is introduced, which has fewer parameters and easy parameter conversions with the HSS model. First, the characteristics of the IGS nonlinear elastic model are presented, and the parameters for the two models are given, by which the IGS model is able to describe the stiffness attenuation at small-strain stage, the stress-strain relationship at large-strain stage and dilatancy with limited parameters. Then, a case study on Dongfang Road Interchange Project in Shanghai is carried out. The calculated results show that the similar results by the two soil models verify the feasibility of IGS model for numerical simulation of excavation. However, the IGS model overestimates the small strain stiffness, which leads to slightly smaller results. The calculation with both the Overlay model and the IGS model can give estimations in rational range.