Research On Deformation Effect And Control Of Metro Shield Tunnel Passing Under Existing Highway Tunnel

In recent years,with the enhancement of China's economic strength,the rapid development of China's subway transportation construction,coupled with the scarcity of underground soil resources,the construction of new subway tunnels often crosses existing highway tunnels,and at the same time Safety accidents occur frequently.For this reason,it is very important to study the influence and control of the deformation of subway tunnels under existing highway tunnels.This article takes the newly constructed shield tunnel under the Jinyuan Road tunnel between the Xiaojinzhong Station and the Yunxi Park Station of Guangzhou Metro Line 12 as the engineering background.The theoretical analysis,numerical simulation and artificial neural network methods are used to penetrate the shield.Conduct systematic research on the influence of tunnel construction deformation,summarize the deformation law of the shield tunnel under construction on the surface and the existing tunnel structure,and optimize the construction parameters of the pressure of the tunneling surface,grouting pressure and grouting layer to control the settlement of the tunnel structure Finally,the BP neural network that can accurately predict the settlement of the construction structure under the shield tunnel under different construction parameters is compiled.The main conclusions are as follows:(1)Use the Midas GTX finite element software to establish a three-dimensional model of dynamic construction of the shield under the existing tunnel.The diameter of the left and right shields of the new shield tunnel is different.In this case,the lateral settlement of the existing highway tunnel structure is "Double wave valley shape",the largest settlement is above the center line of the large shield;the width of the soil settlement groove caused by the shield excavation is about 40 m,so the buildings and auxiliary facilities within about 40 m on both sides of the shield excavation,In particular,buildings directly above the excavation of the shield tunnel need to strengthen the monitoring frequency and take corresponding protective measures.(2)The single factor control variable method was used to study the influence of the driving pressure,grouting pressure and grouting layer thickness on the tunnel structure settlement during the underpass construction of the shield.It was obtained that the pressure of the driving surface should be slightly greater than the excavation in the setting of the construction parameters The surface static water and earth pressure,the grouting pressure should not be too large under the premise of ensuring the full mixing of the slurry,and the minimum simultaneous grouting volume should be set to fill the gap of the shield tail to reduce the tunnel structure settlement.(3)Based on the orthogonal test plan,the driving surface pressure,grouting pressure and grouting layer thickness are used as input layers,and the existing tunnel structure settlement,surface settlement and segment settlement are used as output layers.Under the parameters,the BP neural network underneath the construction structure settlement of the shield tunnel improves the risk resistance of the project and can be used to guide the adjustment of dynamic construction parameters of similar projects.