The Numerical Simulation Research On Face Stability In Shield Tunneling

Shield tunneling method has become the most primary method in underground excavation with its predominance, and earth pressure balanced shield tunneling(EPBS) is one of the most universal type. Duo to variation of soil conditions and uncertainty in construction, the actual support pressure vary continuously in earth pressure balanced shield tunneling. Therefore, it is of practical significance to study the effect support pressure on soil deformation and elicit the limit support pressure.The paper developed the following work and research according to the related circs:1. Introduce the work principal of the earth pressure balanced shield tunneling and environment effect during excavation, and then bring foreword the significance to study the face stability in shield tunneling.2. According to the characteristic and need of the research, choose appropriate calculate program and constitutive model , and then design the numerical simulation of the research on face stability in shield tunneling.3. Upbuild numerical simulation model for both sand and clay and investigate the rule of soil deformation with the variety of the support pressure. Then put forward the means of obtaining the limit support pressure according to stability mechanism. Discussing the law of settlement induced by low support pressure and the sate of soil deformation after collapse is also very important in the paper.4. Sensitivity studies of tunnel overburden, diameter and soil parameter for the limit support pressure and ground settlement are carried out in this paper. The result show that the larger overburden or diameter, the larger minimized support pressure. When the overburden is shallow, the largest ground settlement site probably have a half diameter distance from the face. The soil friction angle have a strong impact on limit support pressure and collapse state. Different factor educe different influence, and we should take into account this in construction.