承压富水地层地铁车站基坑降水与回灌施工渗流稳定性及地面变形研究

Seepage Stability and Ground Surface Deformation in Metro Station Foundation Pit Dewatering and Recharge Construction in Confined Water-rich Stratum

结合实时监测数据,分析济南某富水承压基坑周边地面沉降以及地下水渗流等主要影响因素。采用有限元数值分析方法建立车站端头基坑的三维地下水应力-渗流耦合有限元模型,分析地铁车站在考虑开挖-降水-回灌情况下的渗流稳定性。研究结果表明:随着基坑的开挖与降水过程的持续进行,周边地层在距基坑10~20 m处的沉降呈现明显凹槽;回灌能在一定程度上恢复地下水的原本渗流,减缓由降水带来的地面沉降,且随着回灌井距离基坑位置的不同而呈现出不同的效果;过近回灌带来的地下水升幅具有危害性,过远回灌则导致恢复地下水渗流效果不理想。模拟结果显示,在距离基坑约30 m处进行回灌,能最大限度地控制地面变形情况且不使基坑过度变形。

Based on the real-time monitoring data,the main influencing factors such as land subsidence and ground water seepage around a water-rich confined foundation pit in Ji’nan are analyzed.A three-dimensional ground water stress-seepage coupling finite element model of the station end foundation pit is established by using finite element numerical analysis method,and the seepage stability of the metro station under the condition of excavation-dewatering-recharge is analyzed.Research results show that:with the excavation of the foundation pit and the continuous dewatering process,the subsidence of the surrounding stratum presents obvious groove 10-20 m away from the foundation pit.Recharge can restore the original seepage of ground water to a certain extent,slowing down the land subsidence caused by precipitation,and showing different effects with different relative locations of the recharge well from the foundation pit.The ground water rise caused by too close recharge is harmful,and too far recharge will lead to unsatisfactory effect of ground water seepage recovery.The simulation results show that recharge at a distance of about 30 m from the foundation pit can maximize the control of land subsidence and avoid excessive deformation of the foundation pit.