Effect of Soil Mechanical Properties on Shield Tunnel Deformation

Surcharge load frequently threatens the serviceability and even safety of urban metro shield tunnels by causing excessive deformations and associated structural defects. This paper aims to characterize the development pattern of tunnel deformation under increasing surcharge load considering the effect of random migration and mechanical properties of tunnel surrounding soil. For this purpose, a meso-scale discrete element model is developed to delicately simulate the macro- and meso-mechanical behaviors of soil-tunnel interaction system. The numerical simulation results show that tunnel transversal convergence develops in a nonlinear growth trend with the increase of surcharge load. This trend is accompanied by a certain degree of dispersion due to random movement of granular soil. Moreover, soil parametric sensitivity analysis is carried out. The results demonstrate that soil elastic modulus plays a role in affecting the overall trend of tunnel transversal convergence, while the internal friction coefficient of soil has influence on the variability. Results from the numerical model are compared with real data and show the promising possibilities of the model to predict tunnel deformation under varying load conditions.

Keywords: Soil-tunnel interaction, mesoscopic analysis, discrete element method, shield tunnel, transversal convergence.