Study On Deformation Behavior Of Foundation Pit Of Jinan Near Reservior Based On Fluid-solid Coupling

Foundation pit engineering is the foundation of all construction projects an d an important part of underground engineering.In some adjacent areas with h igh groundwater level,dewatering measures should be taken to reduce the grou ndwater level below the bottom of the foundation pit to ensure that there is n o groundwater seepage above the surface of the foundation pit before excavatio n.The process of dewatering and excavation will change the stress field and se epage field-fluid-solid coupling effect around the foundation pit,and the fluid-s olid coupling effect in the foundation pit will cause the deformation of the sur rounding soil and retaining structure of the foundation pit.When the deformati on is too large,it will destroy the foundation pit itself and adjacent buildings.I n order to ensure the safe construction of the foundation pit,it is necessary to study the fluid-solid coupling problem in the foundation pit.This paper relies on the deep metro foundation project of Mengjiazhuang St ation of the R3 line of Jinan City,collects and collects the risk sources and h ydrogeological environment data around the foundation pit of Mengjiazhuang St ation,and uses monitoring data analysis,numerical simulation results and actua l measurement comparison methods.Using Visual Modflow groundwater simulat ion software and Flac~3DD finite element analysis software,the influence of defor mation law of foundation pit excavation process and groundwater seepage on t he stability of foundation pit is systematically analyzed.The main contents are as follows:(1)Based on the analysis of the project conditions,on the basis of analyz ing the surrounding environment,hydrogeological conditions and supporting for ms of the project,the contents and monitoring methods needed for monitoring the foundation pit project are formulated.It mainly monitors the ground settle ment,the horizontal/vertical displacement of the surrounding pile,the deep hori zontal displacement of the pile,the groundwater level.The monitoring data is analyzed and analyzed,and the deformation lawofthe foundation pit excavation process is obtained.(2)For the actual project of the foundation pit of Mengjiazhuang Station,the precipitation process under different water cut curtain depth,precipitation w ell depth,precipitation well pumping capacity,layout backfilling well,Mengjiaz huang Reservoir flood season and dry season water level The seepage analysis was carried out.By analyzing the precipitation effect and seepage law under di fferent groundwater control measures,it was found that the water curtain depth was 27m,the depth of the precipitation well was 23m,and the single well pu mping volume was 110m~3/d.(3)The main pit of Mengjiazhuang Station is located in the strong perme able gravel soil layer.The groundwater in the gravel soil layer is connected wi th the Mengjiazhuang Reservoir in the west.The groundwater level in the stro ng permeable layer can be considered to change continuously with the seasonal fluctuation of the reservoir water level.The period and frequency are the sam e but there is a certain phase difference.By analyzing the influence of the wat er level of different reservoirs in the flood season and dry season of Mengjiaz huang Reservoir on the seepage of groundwater around the foundation pit,it is found that the water level of the Mengjiazhuang Reservoir is 0m,and the gro undwater level around the foundation pit is the highest.(4)The depth of the water curtain is 27m,and the depth of precipitation is 0.5m below the bottom of the foundation pit.Three internal supports are us ed to analyze the fluid-solid coupling of the whole process of precipitation exc avation,and the foundation of the main reservoir in the gravel layer is obtaine d.The law of pit degeneration is basically consistent with the actual monitorin g data,which verifies the rationality of the numerical simulation.And compari ng the actual monitoring data with the numerical simulation results without con sidering the seepage effect,it is found that the phase difference is large,and it can be considered that the groundwater seepage effect is more in line with th e actual situation and cannot be ignored.(5)Based on the different water levels of the foundation pit during the fl ood season and dry season of the reservoir,the finite element simulation softw are Flac~3DD is used to establish the fluid-solid coupling model of foundation pit excavation and precipitation,The variation of stress field and seepage field of the retaining structure under the joint action of excavation and precipitation is obtained.Deformed cloud map.It can be obtained that whenthe initial water lev el of the foundation pit is 0m,the deformation of the foundation pit is the lar gest,and the point where the surface settlement is the largest is located 3m a way from the center of the foundation pit.The maximum horizontal displacem ent of the pile is less than 1m at the upper end of the pile.