Numerical analysis for the role of soil properties to the load transfer in clay foundation due to the traffic load of the metro tunnel

Abstract

Soil properties play important role to the metro tunnel settlement induced by traffic load of metro operation. Numerical studies on this topic are still rare due to the lack of accurate dynamic constitutive models of clay. In this study, a new critical state based bounding surface plasticity model for natural structured clays is first developed. It is able to consider the initial and induced anisotropy of natural clay and the structure disturbance to the initial size of yield surface and to the initial adhesive stress by cyclic loading at low-stress levels. The applicability of the present model is evaluated through comparisons between the predicted and the measured results of numerous stress-path tests on Shanghai clay and Vallericca stiff clay. The model is then implemented as a user-defined model in a finite difference code. A typical tunnel in clay is simulated using the implemented model coupled with Biot's consolidation, for which the stress distribution pattern in subsoils around tunnels due to train movement is investigated. The role of the dynamic constitutive model has been highlighted by comparing the simulation results of a static constitutive model and a dynamic constitutive model. The influences of the soil properties such as the anisotropy, structure ratio, and adhesive mean stress have been found significant to the load tranfer.