Study On Deformation Characteristics Of Foundation Pit Excavation Of A Metro In Shenzhen And Analysis Of Landslide Causes

Shenzhen is located in the South China Sea.Mud and sandy soil layers are the main areas in Shenzhen.At the same time,the coastal areas are infringed by groundwater and heavy rainfall.Taking the foundation pit of a subway station in Shenzhen as the engineering background,the deformation and landslide accidents of the silt-type super-long foundation pit excavation in Linhai are analyzed by combining monitoring data and numerical simulation.The main contents and results are as follows :The deformation of diaphragm wall during excavation of foundation pit is compared and analyzed in terms of groundwater seepage,heaped load outside the pit and overexcavation.Consideration of groundwater seepage greatly affects the displacement deformation of diaphragm wall.In addition,heaped load at the edge of the pit causes the horizontal displacement of the wall to increase and the position of the maximum displacement to rise.Overexcavation also increases the horizontal displacement of diaphragm wall and decreases its maximum displacement position.Then,the influence of slope height,top load,top load distance and load length on slope stability is analyzed by traditional slice method;the first two do not have a fixed range of influence,while the latter two only affect slope stability in a certain range;the soil strength decreases before and after rainfall is simulated by Midas GTS,and the excavation depth and external load are changed at the same time.Finally,through the orthogonal design and grey relational coupling analysis,it is concluded that rainfall is the main cause of the accident,while mechanical load on the top of slope and unreasonable excavation are the other causes of the accident.