Study On Ground Deformation Mechanism And Numerical Simulation Caused By Pipe Jacking In Deep Soft Soil

The development of China's economy and the advancement of science and technology have led to the substantial advancement of the urbanization process and the rapid development of pipe jacking construction technology.However,it is very difficult to completely avoid the impact of the pipe jacking construction on the surrounding soil.If the construction of the pipe jacking is improperly controlled,it will endanger the surrounding environment,especially in the construction of the pipe jacking in the deep soft soil layer with poor soil structure.Therefore,this paper relying on the pipe jacking project of sanyang wetland section of the 220 kv substation transformation project in shangtian of wenzhou city,numerical simulation study on the pipe jacking construction across deep soft soil layer is carried out with the help of FLAC 3D software,which can Provide guidance and reference for construction of the project and similar construction.The main research work and conclusions of this paper include:(1)By referring to the relevant literature and combining with the field practice experience,the soil disturbance and ground deformation caused by pipe jacking construction are analyzed.It is believed that the main cause of soil disturbance and ground deformation is formation loss.(2)Combining the geological survey report,analyzing the engineering geological and hydrogeological characteristics of the pipe jacking construction site,obtaining the shear strength index of the soft soil through the UU triaxial test,and causing the pipe jacking construction in the deep soft soil layer according to the monitoring plan.The ground subsidence is monitored and the ground subsidence law is obtained.(3)Using FLAC 3D software to establish a numerical model to simulate the pipe jacking construction,study the ground subsidence law,and compare the results with the settlement law of the pipe jacking construction site.The results show that: The simulated subsidence curve is basically consistent with the monitored land subsidence curve,which verifies the accuracy of the model.(4)Based on the original numerical analysis model,the change law of soil horizontal displacement is analyzed.The maximum horizontal displacement of soil mass lies in the buried depth of pipe jacking axis.The horizontal displacement of soil at the top and bottom of the pipeline is 2.96 mm and 3.16 mm.When the excavation surface is 2D away from the measuring point,the horizontal displacement of soil increases significantly.When the excavation surface is 2D away from the measured point,the increase rate of horizontal displacement of soil gradually decreases,and the final displacement value tends to be stable.(5)Based on the original numerical analysis model,if the pipe diameter,buried depth and elastic modulus of soil are changed,the soil settlement law caused by pipe jacking remains unchanged.The maximum settlement value appears at the crown of pipe jacking and the maximum uplift value appears at the bottom of pipe jacking.Reducing pipe jacking diameter or increasing buried depth of pipe joint can reduce soil disturbance and ground deformation.The larger the elastic modulus of soil,the greater the stiffness of soil,the greater the bearing capacity and resistance to deformation of soil,more conducive to reducing soil disturbance,reduce the value of ground deformation.