Study On Ground Subsidence Caused By Earth Pressure Shield Construction Of Double-line Tunnel In Soft Ground

With the development of subway project,there are more and more limiting factors in the construction of subway.The traditional single line tunnel can not meet the needs of social development,and the two-lane tunnel has got more and more applications because it could balance the cost and traffic.There are few researches on surface subsidence caused by shield construction of double tunnels in the present research results,Superposition of the settlement curve of two single line tunnels has been used to predict the surface subsidence caused by double tunnels.However,the simple superposition of the settlement curve can not accurately reflect the development of surface subsidence because of the mutual influence in the construction of two tunnels.Therefore,it is necessary to study the ground subsidence law caused by shield construction of double line tunnel.Changzhou Metro Line 1 uses the typical double line tunnel section form,and the project is located in the middle and lower Yangtze River,the tunnel area belongs to the soft soil ground.This paper studied the ground subsidence law caused by earth pressure shield construction of double line tunnel in soft soil site through the field monitoring and FEM analysis.The main work is as follows:(1)According to the monitoring data of 6 monitoring sections in the project,combined with geological conditions and construction parameters,the surface subsidence caused by shield construction in Changzhou Metro Line 1 are analyzed.In addition,the paper analyzes the surface subsidence curve of the double line tunnel project,and summarizes the distribution law of the ground subsidence trough caused by the earth pressure shield construction of the double line tunnel,and the curve of surface subsidence groove of double-line tunnel has the characteristics of diversification and complication.(2)According to the engineering geology data and the design document,the software Abaqus and the Mohr-coulomb elastic-plastic yield criterion are used to simulate the construction process of the earth-pressure shield of the double-line tunnel,and the calculation formula of grouting pressure is introduced to improve simulation of grouting process.The correctness of the model is verified from two aspects of the land surface subsidence transverse distribution and the surface subsidence development process.While validating the model,the law of surface subsidence is supplemented and a complete surface subsidence curve is obtained.(3)On the basis of the existing model,the influence of three factors,such as tunnel spacing,grouting pressure and soil pressure,on the ground subsidence law caused by shield construction of double line tunnel is studied numerically.At the same time,the recommended value of grouting pressure,soil pressure and tunnel spacing in the construction process of earth pressure shield of double line tunnel is given by combining the design code of metro and the existing research results.