Design And Application Of Shield Tunneling Simulation System

Due to the little influence on road traffic and surrounding buildings, and less time in construction, shield tunneling is popular in tunneling. But it is inevitable that shield tunneling will affect surrounding soil and cause ground settlement. Therefore, the study of the influence of shield tunneling on surrounding soil is conducive to improve the safety of tunneling.Based on elastoplastic mechanics, finite element program of elastoplastic problem is generated by FEPG (Finite Element Program Generator) system. And the program of elastoplastic problem is further developed to numerically simulate shield tunneling, according to practical process of shield tunneling. The simulation takes into account all relevant components of the construction process (the slurry pressure and the release of stress at the excavation face, the time dependence of the grout material characteristics, the grout pressure and the taper of shield skin).Furthermore, an interface program for preprocess and postprocess of the finite element program is developed by means of GID's customized features and TCL / TK programming language. The interface program simplify the complicated process of simulation of shield tunneling by providing a user guide to help users set parameters related to shield tunneling step by step. Finite element model, grid, boundary condition and loads of the numerical simulation will be automatically generated after the completion of user guide. In addition, the guide interface also helps to generated subsidence curve and analyzes the stability of solid at excavation faceFinally, a 3D nonlinear finite element model is presented to simulate Chongming river-crossing shield tunneling in Shanghai. The ground settlement by numerical simulation is validated by the comparison with field measurements, which shows the rationality of this simulation method. The influence of main factors (the slurry pressure, the grout pressure and the depth of tunneling) causing ground settlement is studied through numerical simulation. Because of the important influence of the soil heterogeneity on the ground settlement during shield tunneling, the mechanics parameters of each element are set according to a certain statistical distribution to create a 3D finite element model of a heterogeneous soil, and the analysis of the influence of the heterogeneity is also presented. From impact analysis, the possibility of overdue ground settlement and instability at the excavation face can be predicted and avoided by optimization of tunneling factors to improve the safety.