Analysis Of Deformation Law Of Deep Foundation Pit Caused By Dewatering Based On Finite Element Method

With the rapid development of our country’s economy,the requirements for the use of underground space are urgent.The excavation depth of foundation pits is getting deeper and deeper,and the excavation of deep foundation pits must ensure that there is no water or water in the pit but does not affect the construction.Dewatering is one of the main methods.1.Foundation pit deformation and seepage damage caused by precipitation account for 90% of the total number of foundation pit accidents,and precipitation has become a key factor in foundation pit excavation.When the foundation pit is insufficiently dewatered,it is difficult to ensure the smooth construction of the foundation pit.When the foundation pit is excessively dewatered,it may cause excessive settlement and deformation of the surrounding stratum and cause accidents.Therefore,it is necessary to study the law of stratum deformation caused by precipitation.This paper takes a deep foundation pit dewatering project in Changchun as the research object.Through theoretical calculations,monitoring data and numerical simulations,multiple examples of foundation pits are analyzed to obtain the law of ground deformation caused by precipitation in Changchun area.For reference,the main work and results of this article are as follows:(1)Collect and consult domestic and foreign literature on foundation pit precipitation and finite element research,summarize and analyze,and point out the regional characteristics of formation deformation caused by precipitation.(2)A comparative analysis of common foundation pit precipitation forms and advantages and disadvantages in Changchun area,introduction of Terzaghi consolidation theory,Biot consolidation theory and the coupling relationship between seepage field and stress field,analysis of theoretical calculation methods of formation deformation caused by precipitation,Laws and influencing factors.(3)Theoretical design of a deep foundation pit dewatering project in Changchun,and theoretical calculation of its soil settlement value,and comparison and analysis with the foundation pit monitoring data,to obtain the empirical coefficients of layered settlement of different soil layers caused by precipitation and the area’s The overall settlement experience coefficient Ψw∈(0.07,0.15).(4)Using Midas GTS NX finite element calculation software to analyze theconstitutive model,it is concluded that the modified Mohr-Coulomb constitutive model is more consistent with the simulation results of the surrounding soil settlement and deformation under precipitation conditions.The main parameter compression modulus ES,which is the difference between the numerical simulation and the monitored value,is simulated and analyzed,and the numerical simulation result is basically consistent with the monitored value when the compression modulus ES is 10～15 times;the different precipitation is adjusted and adjusted through multiple foundation pits The depth obtains the influence zone of deformation caused by precipitation in Changchun area,and obtains the influence relationship between the maximum surface settlement value ΔS and the water level drop SW.(5)Combining the deep foundation pit example project,by adjusting the dewatering method,the spacing of dewatering wells,and the depth of the water level,the deformation of the foundation pit caused by dewatering is studied.It is concluded that the layered dewatering method can reduce the surface settlement value.6～8m is suitable,the increase rate of surface settlement decreases with the increase of water level drop.