Numerical Simulation Analysis Of Deep Foundation Pit Excavation Under Dewatering Condition

With the rapid development of cities,the construction of subway in China has sprung up,many engineering accidents have also occurred along the way.The accidents of foundation pits caused by the groundwater problems are also unstoppable.In the process of watering of the foundation pit,If the precipitation is not operated properly,it will cause the deformation of the retaining structure,the settlement of the foundation and the near foundation of the building,the cracking of the wall,the destruction of the roads and underground pipelines and so on.There are many factors that cause settlement and deformation around foundation pit during construction,and there are even some factors that interact with each other,it may plays a crucial role in foundation settlement,how can we reasonably and comprehensively consider the influencing factors in the process of foundation pit construction,it is an urgent problem to be studied and solved..In order to study the influence of various supporting structure parameters on foundation pit during the process of foundation pit watering,this paper elaborates on the theoretical research on the foundation pit watering method,the type of foundation pit failure,and the watering mechanism of the foundation pit,the finite element software MIDAS GTS/ NX is applied to simulate the construction process of foundation pit,using the data processing software Origin to compare the simulation results,optimizing the parameters of the support structure reduces the impact of precipitation on the deformation and foundation settlement of the foundation pit support structure,the conclusions are as follows:(1)The influence of foundation pit precipitation on the project must be considered when excavating foundation pits in areas where groundwater is present.Precipitation will increase the deformation of support structures such as walls,floors,lattice columns,etc,especially for the near ground area of foundation pit,the effect of precipitation on ground settlement in the vicinity is 10 times that of no water,Precipitation can not be ignored for ground settlement.Therefore,when excavating foundation pits in areas with higher groundwater levels,necessary measures must be taken for underground pipelines and buildings near the excavation area,prevent the destruction of the pipelines and buildings in the foundation pit and adjacent strata due to the reduction of groundwater level.(2)As a result of a series of reasons in the construction process,the original design stress value in the brace is reduced,which may also be the cause of various non-permanentloads in the construction,resulting in the reduction of internal stress value of the brace after the final construction.The horizontal displacement of diaphragm wall toward foundation pit is confirmed by the change of bracing internal force.The research on the development law of horizontal displacement of diaphragm wall toward foundation pit can proceed from the change of bracing internal force.During the initial stage of earthwork excavation,the horizontal displacement of the top of diaphragm wall varies greatly in a certain period of time.It is necessary to strengthen the monitoring and measuring of representative position points in the process of earthwork excavation.It is necessary to analyze the monitoring and measuring data of horizontal displacement of the top of diaphragm wall on time and in quantity every day,and to be alert to the underground connection at all times.The change rate of horizontal displacement of the top of the retaining wall can not appear too fast,so as to control the stability of the foundation pit in advance and do a good job of remedial protection measures.With the continuous progress of earthwork excavation and the increasing depth of foundation pit,the deformation of diaphragm wall increases continuously.At the same time,with the construction of supporting structure in various stages,it is found that the horizontal displacement of diaphragm wall will appear and the whole change will occur at the position of 9-11 m below the top of foundation pit slope.The trend is small in the middle and big in both ends.It is found that the numerical value of numerical simulation is smaller than the actual monitoring value of the project.For this reason,it may be that the complexity of the soil layer or the construction load on the top surface of the foundation pit are not taken into account in the numerical simulation process,or the value of the elastic modulus is not accurate enough.