Experimental Studies Of Tube Well Dewatering Outside The Foundation Pit In Taiyuan Metro Station

To alleviate traffic pressure and improve people’s travel conditions,the subway is being built in Taiyuan.In the past,the foundation pit scale of Taiyuan was small and mostly constructed by open cut method,almost all of them were treated with curtain water plugging method,Groundwater control methods are relatively simple,The underground water control of the subway project is very different from the conventional building,Influence of large or complex hydrogeology area in groundwater,because the station interval station space span is relatively large,especially in the horizontal direction span several kilometers to dozens of kilometers,with pure water blocking method is very difficult,and subway construction in urban areas,most of them use subsurface excavation method,the underground continuous wall constructed by the curtain water seriously restricts the application of the underground excavation method,Dewatering method should be the best choice to control ground water.This paper takes Taiyuan 2 line subway Jiajie station as an example,adopt the method of tube well dewatering outside the foundation pit for groundwater control study,to explore the foundation pit dewatering that the feasibility of the control method in Taiyuan formation of groundwater.The study both on perfecting the control method of groundwater in Taiyuan,or on the follow-up guidance for the construction of subway line of Taiyuan,has very important practical significance.Through the engineering dewatering test,relying on single well pumping test,well pumping test and surface subsidence monitoring data,the following conclusions are drawn:(1)By means of analytic method and Visual Modflow numerical simulation inversion method,the permeability coefficient of the study area is calculated and analyzed.The range of the parameter is 4.08-17.26 m/d,The coefficient of permeability of 2-5 middle sand and 3-4-1 viscosity-soil layer is 10 m/d,and the permeability coefficient of 3-5 powder sand aquifer is 4m/d;(2)Using the analytic method and the MIDAS/GTS fluid-solid coupling model,the final sedimentation of the surface area of the site was calculated,Its value is-25.4mm,-26mm,Compared with the maximum settlement value-15.58mm,the calculation results show that the ground surface settlement accounts for about 60%of the total settlement,and the maximum uneven settlement rate is 0.7 per thousand at the same time,and the rate of uneven settlement is smaller;(3)In the original design scenario,the water level at the north and south end of the station was not up to standard,and two sets of optimization schemes were designed by adjusting the distance between the wells and changing the pump volume,Finally,the layout of the scheme is 94 wells,pumping capacity 3m~3/h,well spacing 6m,pumping time 12d is the best precipitation program.Based on the above research,it is considered that the method of groundwater control for out of foundation pit is feasible in Taiyuan similar stratum.