Study On Structural Stress And Deformation During The Construction Of Semi-cover Excavation Of Subway Station

In recent years,the development and utilization of urban underground space is faster and faster,and underground rail transit has developed rapidly.However,the construction of subway lines is often restricted by factors such as large traffic flow,many pipelines,and dense buildings.To meet the normal operation of traffic and ensure the progress of the project and save the construction cost,the half-cover excavation method has been gradually applied to the foundation pit engineering of a subway station.Half covered excavation method from Ming excavation method and covered excavation method developed on the basis of,but its structure is different from the two methods,this article based on Ningbo subway station foundation pit engineering,using theoretical analysis,field measurement and numerical simulation method research station half-covered excavation method of foundation pit construction in the process of structure deformation characteristics of the specific research work and the results are as follows:(1)By analyzing the characteristics of subway station foundation pit engineering,the force analysis model of half-cover excavation foundation pit structure based on the incremental method is established,and the internal force variation rule of the cover plate and ground wall in each excavation stage is calculated.Because the foundation pit is affected by the bias of vehicle load,the stress on the ground wall of the covered excavation side is obviously greater than that of the open excavation side.(2)The field measured force deformation of the foundation pit structure during the construction process of the half-cover excavation method.The results show that the temporal and spatial characteristics of horizontal displacement of the ground wall,uplift of the middle column,surface settlement of the pit side,and axial force of support are significant,and the displacement deformation on both sides of the foundation pit has obvious asymmetry.(3)ABAQUS finite element analysis software was used to simulate the structural stress and deformation during the construction of the subway station half-cover excavation.The displacement variation trend of the calculated foundation pit retaining structure was the same as the measured results,which verified the reliability of the numerical model.(4)The internal force analysis of the half-cover excavation structure is carried out to obtain the safety and stability coefficient of the envelope structure.On this basis,the critical muck truckload on the cover plate is determined through a simulation study.The analysis shows that the displacement and deformation of the envelope structure under this load meet the requirements.(5)because of the deformation characteristics of the foundation pit in the construction of the half-cap excavation method,the excavation method of the foundation pit is optimized and the influence of different support erection methods is studied.The new excavation method is beneficial to control the deformation and can save the cost by reducing the support stiffness.The overall downward movement of the bottom steel support is beneficial to controlling the displacement and deformation of the ground wall.Support should be erected in time to avoid excessive deformation of the foundation pit caused by lag.