| At present,the construction problems of foundation pit are becoming more and more prominent,In order to effectively grasp the progress of construction,improve the influence of precipitation excavation on the construction of the foundation pit and alleviate the impact of the foundation pit on the surrounding environment,this paper select a foundation pit of a moving-back building,which is an urban village remolding project with a relatively typical construction environment,as the object of analysis.The influence of precipitation excavation on the surrounding ground of the foundation pit is analyzed in detail through performing its simulation.This can make a reference to the smooth construction of this pit foundation project,and gain experience for the next step of construction.In order to study the influence of various parameters on the surrounding environment,this paper introduces the basic theory of groundwater seepage and the theory of foundation pit drainage.The model is established by FLAC3 D,and the effect of the relevant parameters is calculated by the method of fluid-solid coupling.(1)Taking a foundation pit project in Taiyuan as the object of study,According to the results of geotechnical survey and the report,the FLAC3 D finite difference software is used to compare the pore water pressure,horizontal displacement and vertical deformation of the foundation pit after excavation and precipitation.Then the numerical simulation results are compared with the actual monitoring results.(2)The numerical simulation analysis of the foundation pit project in Taiyuan is carried out considering flow solid coupling.The FLAC3 D program is used to analyze the deformation of the ground pit caused by the engineering precipitation,then analyze the influence of many factors including the depth of the curtain,the depth of the pumping well,the well spacing,and the number of recharge wells on the ground deformation of the surrounding pit.Based on the above analysis,following conclusions are obtained:(1)Foundation pit precipitation makes soil pore water pressure gradually decrease,forming a shape like "precipitation funnel".The pore water pressure of the foundation pit decreases slightly under the action of water stopping curtain.The excavation process has no effect on the change of the pore water pressure outside the foundation pit.(2)The simulated results of ground subsidence and the horizontal deformation of the foundation pit are consistent with the measured values,and the errors are within the allowable range.(3)When the depth of the curtain is changed,the influence of the curtaindepth on the pore water pressure distribution and the vertical displacement inside the foundation pit are negligible during the pre-excavation.Larger the depth of the curtain is,a better effect of stopping water can be got,smaller the settlement and sedimentation range are.(4)When the depth of the pumping well exceeds 18 m,the increase of the pore water pressure in the foundation pit is limited.When the depth of the pumping well exceeds the depth of the curtain,the groundwater outside the foundation flows directly parallelly into the pumping well,so that there is a great settlement of the soil outside the foundation pit.It can be seen only improving the depth of the drainage wells to enhance the effect of foundation pit precipitation is unreasonable in certain range.(5)When the pumping distance is 10 m or 12 m,the distribution of pore water pressure in the foundation pit is basically the same when the pumping is completed.With the increase of the well distance,the pumping capacity will not be able to meet the needs of excavation.Therefore,choosing well distance should be reasonable.However,it can not be concluded that smaller well distance is better.(6)For the installation of recharge wells,the more the number of recharge wells at the bottom of the water curtain,the smaller the pore water pressure change,and the land subsidence.In addition,the layout of the recharging well also reduces the influence area of the settlement. |
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