The Numerical Analysis On The Influence Of The Excavation Of Shaft To Underlying Tunnel

At present,the rail transit has become one of indispensable transportation along with the rapid development of urban construction.Excavation leads to stresses release of local soil,produce the displacement deformation in the direction of the stress release and additional stress and deformation on the adjacent metro tunnel,which may lead to the safety of metro tunnel.How to predict the influence of excavation accurately and reasonable on adjacent metro tunnel has become an issue of urgent need.This paper use finite element software ABAQUS for simulating a vertical shaft excavation,and the main contents are as follows:First,review of rock and soil deformation characteristics,foundation pit deformation theory,introduces the application of ABAQUS in foundation pit engineering,including the rock and soil constitutive model is commonly used,contact theory,the initial ground stress field and foundation pit excavation simulation,etc.Second,the effect of foundation pit excavation on tunnel deformation under the three conditions of same burial depth with different distances to foundation pit,same distance to foundation pit with different burial depths and the tunnels inside of excavation is analyzed by building 8 finite element models through ABAQUS,where the tunnel burial depths are 0.75 H,1.125 H and 1.875 H respectively,the distances between the tunnel to the foundation pit are 0.375 H and 1.875 H respectively(H is the excavation depth of the foundation pit)and the distance between the tunnel and the center of foundation pit are 0 m and 2.4 m under the excavation 5.0 m..Last,combined with a shaft project in Shenzhen,ABAQUS is adopted to establish the three-dimensional finite element model firstly,and then the influence of shaft excavation on underlying subway is analyzed through numerical simulation method.The vertical and horizontal displacement of tunnel at different excavation step,resilient deformation of the soil at the bottom of the shaft,vertical displacement of the tunnel axial center cross section at different excavation depth and the plastic strain of soil around the tunnel are analyzed.