Research On The Influence Of Excavation On He Behavior Of Adjacent Tunnel Based On Back Analysis

With the development of underground space,More and more excavations are adjacent to the existing tunnels.Excavation will change the stress field distribution of the foundation adjacent to the tunnel,which will induce additional deformation of the tunnel,causing damage to the tunnel;In addition,the uncertainty,non-linear and time variation of the soil parameters will also cause difficulties in real-time assessment of the foundation and tunnel properties.Therefore,selecting reasonable soil parameters and predicting the deformation of the tunnels induced by adjacent excavation have very important significance.Based on the investigation and analysis of a large number of engineering cases,aiming at the problems of selecting soil parameters of the finite element analysis software,which is used to simulate the construction process of the excavation and analyses the surrounding underground structures,real-time parameter inversion,orthogonal tests,MIDAS GTS software,genetic neural network and other methods are used to determine the soil parameters,statistical of the on-site displacement monitoring data and theoretical analysis is used to analysis the displacements of the tunnel.main research contents and conclusions are as follows:(1)The statistics cases have been collected in which the foundation pits are adjacent to the tunnels.the soil characteristics of tunnel are summarized,and the deformation characteristics of the tunnel are analysed.(2)tunnel is simplified as an Timoshenko beam,The two-stage method is used to calculate the horizontal and vertical additional displacement of the tunnel caused by the excavation of the side wall and bottom of the pit.The effects of different excavation depth,tunnel depth,horizontal distance between the foundation pit and the tunnel,and the coefficient of the foundation bed on the displacement of the tunnel are studied(3)This article unifies engineering project,the sensitivity analysis range method is used to determine the sensitivity of soil parameters and obtain the inverted parameters.The orthogonal test table is used to design the soil parameter combination,and the tunnel displacements are calculated based on the finite element software,which is used to train the GABP network.Based on the on-site displacement monitoring data,genetic neural network is used to invert the soil parameters on a case-by-case basis,and the displacement of the tunnel is predicted to analyse the impact of subsequent excavation on the tunnel.