Applicability Test And Analysis Of Pensile Curtain For Water-rich Sand Stratum

China's urban rail transit construction is in the peak period,which is mainly based on underground engineering.While groundwater control has become the key to the design and construction of underground engineering at home and abroad.On the process of construction,under the premise of the economic and technical rationality conditions,the effective control of the impact of foundation pit on the surrounding environment has become an important subject of urban underground construction.According to the different depth of the curtain,it can be mainly divided into the following two: drop waterproof curtain and pensile curtain.Under the premise to meet the anti-seepage pit length,bursting instability and stability requirements,the amount of water in the pit is acceptable and the surrounding environment is controllable.At present,there is not much research on the pensile curtain for water-rich sand stratum,and the stratigraphic hydrogeological parameters are not accurate.So,in this thesis the in-situ pumping test has been carried out,and study the influence of the setting conditions and precipitation design of pensile curtain on project implementation and surrounding environment based on the theory of seepage field.And take a variety of influencing factors into account.Verify the correctness and accuracy of the numerical model by comparing the results obtained by numerical simulation with the field measured data,and make a comprehensive analysis of the economy,which provides a reference for subsequent design.The main work and major results are as follows:Firstly,set up two test zones at test site selected,design and implement single well and well group pumping test.Simultaneously,monitoring the water depth of each observation well and the surrounding surface subsidence during the test.Combined with parametric analysis software Aquifer Test,hydrogeological parameters are obtained.The parameters such as permeability coefficient,water conductivity coefficient and water storage coefficient of each aquifer are preliminarily determined,which provides input conditions for subsequent numerical calculations,and find the hydraulic linkages between the aquifers.Secondly,based on the Darcy's Law and mass conservation law,on the level of micro unit,the governing equations of the three-dimensional seepage field are established.And determine the required calculation parameters and the definite conditions.Numerical modeling is implemented in Visual Modflow,compare and analyze the effects of different influencing factors,such as the depth of pensile curtain,relatively impermeable layer and the design of precipitation wells,on the effect of precipitation and the surrounding environment.Finally,modeling the actual implementation of the site,and compare with monitoring data,to verify the correctness and accuracy of the model.And study the economic and applicability of the promotion and analysis,which provides the theoretical basis and reference for the design of the pensile curtain of similar strata.