The Optimization Of The Groundwater Control Scheme Of The Subway Station And The Environment Impact Analysis Based On Numerical Simulation

Metro as underground engineering is influenced by groundwater inevitably under the construction.Thus the control of groundwater is the top priority of subway construction.The methods of controlling groundwater divide into two main types,named dewatering and water-tight.Although dewatering is widely applied,but usually cause some environmental problems,such as groundwater resource waste,ground subsidence,settlement deformation of surrounding pipelines and buildings.Summarizing the results found at home and abroad,the study on the settlement caused by dewatering focuses on three-dimensional flow model coupled one-dimensional consolidation model,and when calculates the soil's consolidation settlement mainly use the empirical formula.In view of the above problems,the paper uses three dimensional fluid-solid coupled model to study the environmental problems caused by detwatering based on the Hongliannanli Subway of the line 16 in Beijing.The Hongliannanli Subway located in gravel layer,containing water.Then we take the group of well pumping test,use the analytical methods to solve hydrogeolic conductivity K,and build three dimensional groundwater flow model to verify the accuracy of the results.The existing groundwater control method is predicted using the groundwater model,and the result is that the drawdown of the station regional aquifer up to 10 m meets the construction requirements and the drawdown of shafts just up to 3m can't meet the construction requirements.After that we adjust and optimize the groundwater scheme.According to the principle of effective stress,when the water head descreased,the stress of soil would increase and the soil layer would be compressed,even endanger the safety of pipelines and structures around.Existing research uses the empirical formula to predict subsidence caused by dewatering,which has some certain deficiencies.And this article uses Midas/GTS software to build a three dimensional model of fluid-solid coupling,study on the surrounding pipeline and the settlement during the process of dewatering Under this scheme,the maximum land subsidence is 23.55 mm,uneven settlement rate of pipeline is 0.03‰.Proposing the contingency plans of underground curtain and groundwater recharge to prevent the occurrence of land subsidence.