Theoretical Calculation And Test Study On Foundation Pit Dewatering And Recharge For Water-rich Stratum In Jinan

The groundwater resources in Jinan are abundant,which has brought great difficulties and challenges to Jinan’s railway transportation construction.The dewatering of foundation pit is harmful to the surrounding environment,which is bad for the protection of spring water of Jinan.Therefore,the groundwater recharge technique is considered,and the extracted groundwater will be pumped into the aquifer in order to ensure that the water level around the foundation pit will not be changed obviously,and minimize the adverse effect on the surrounding environment,and also supply the groundwater.However,the current research of recharge calculation theory and related test is less and immature,and it lacks a complete theoretical calculation system.It is of great practical significance to carry out the theoretical calculation and related test study on foundation pit dewatering and recharge.Based on Jinan rail transit line R1,this paper studied on foundation pit dewatering and recharge calculation theory through theoretical analysis,model test,field test and numerical simulation.Furthermore,the calculation theory was further improved by model test and field test,and finally the results were applied to practical engineering.Major research and related results are as follows:(1)System calculation theory study on groundwater recharge.On the basis of previous studies,this paper supplemented and completed the single-well recharge theoretical calculation formula by establishing the mathematical model of groundwater recharge and to solve and analyze,and also determined the calculation method of recharge influence radius.On this basis,according to the principle of superposition of water flow,further deduced the steady flow and unsteady flow calculation formula of multi-well pumping,multi-well recharge and under the condition of pumping and recharge at the same time.In addition,the recharge calculation formula near the boundary was deduced according to the mapping method,and the existing theory of groundwater dewatering and recharge calculation theory was further improved.(2)The research on laboratory system of indoor recharge model for the typical sandy cobble stratum in Jinan.The model test truly simulated the pipe recharge process and the variation of the groundwater seepage field over time was obtained.Through the analysis of the test data,the unsteady flow calculation theory of pipe well recharge was verified.(3)Regularity analysis of field recharge test and the correction of calculation theory.According to the field recharge test phenomena and data in Jinan area,the paper discussed the rule of pipe recharge in Jinan and analyzed the recharge effect.Aiming at the problem that the actual recharge efficiency is lower than the theoretical value for various reasons,a method to reduce the permeability coefficient in the calculation formula was proposed.The result showed that the permeability coefficient of the actual stratum was two thirds to three quarters lower than the original permeability coefficient.(4)The dewatering and recharge scheme design of a deep foundation pit project in Jinan rail transit line R1.The research of recharge calculation theory was applied to the scheme design of dewatering and recharge of actual foundation pit construction.This paper simulated the variation of groundwater table caused by the dewatering and recharge of the foundation pit by using the numerical simulation software and optimized the scheme.The paper proved the feasibility of the dewatering and recharge scheme of foundation pit through the contrastive analysis of the numerical calculation results and the theoretical calculation results,and also proved the combined calculation theory of pumping and recharge,which provided reference and guidance for actual construction.