Study On The Influence Of Tunneling Disturbance Of Deep-buried Shield Tunnels In Soft Soil

Urbanization in China is witnessed rapid constrctxion of urban infrastructure such as urban rail transit,railway tunnel,water diversion project,river crossing highway and other major projects.Of which,the subway tunnel gradually develops to a large depth direction.Deep buried conditions not only bring new challenges to shield tunnel design and construction,but also profoundly affects the deep development and utilization of urban underground space.Focusing on the recent problems of deep shield tunnel construction design and calculation,this thesis systematically studied the construction control technology and related calculation theory of deep shield tunnel via numerical simulation,indoor geotechnical experiment,and field monitoring methods.The research result offers practical guides for the construction of similar deep shield tunnel projects.It also buids a theoretical base for the safety technical standards of the construction and protection of deep shield tunnels that are built adjacent to existing buildings(structures).The thesis reports the key construction project of the ultra deep Metro Tunnel in Hongmei South Road,Shanghai during the whole operation period of the project.The influence law of the micro disturbance of the surrounding soil as well as the tunnel during the process of the deep shield tunnel crossing is studied to provide suggestions for the project construction.The main conclusions are as follows:(1)Through the field monitoring,it is found that the earth bin pressure greatly affects the lateral settlement tank.With the increase of the earth bin pressure,the formation loss rate decreases;the width of the lateral settlement tank decreases;the earth bin pressure increases;the maximum settlement of the clay stratum decreases gradually;and the decrease amplitude increases.There is a big difference in the maximum settlement under different silo pressures.(2)Through the establishment of a three-dimensional finite element simulation,the research shows that the main deformation of the tunnel structure is vertical displacement.With the increase of the support pressure of the excavation face,the vertical displacement of the tunnel also begins to increase.The influence of the support pressure on the deformation of the newly installed lining segment is limited.With the increase of the support pressure of the excavation face,the deformation of the lining decreases.(3)When the earth pressure increases from 0.2MPa to 0.4MPa,the maximum settlement will reduce by 1% and 5% respectively with respect to 0.2MPa.That is to say,with the increase of soil pressure,its influence on settlement enlarges.In the process of tunneling in soft soil layer,the proportion of sandy soil layer in the surrounding rock of tunnel section increases gradually,which increases the cutter head resistance,the cutter wear speed,and thus the required torque.