深基坑工程多层承压水的抽水试验研究

Study of pumping test in deep excavation engineering with multi-layer confined groundwater

随着基坑深度不断加大,多层承压水的深基坑问题亟待解决。在实际工程中,查明场区岩土体水文地质特性及不同含水层间越流补给关系,获取较为准确的水文地层参数,防止突水、管涌等事故的发生对基坑的安全运行具有重要的意义。本文以常州市某深基坑工程为例,对基坑底部Ⅰa、Ⅰb层承压水进行研究,开展了单井与群井承压水非稳定流抽水试验,将数值模拟的成果与实际观测得到的拟合曲线对比,评价抽水试验获得的水文地质参数的可靠性。根据抽水试验及水位恢复过程中的地表沉降监测结果,预测承压水降水对周围环境的影响,从而为减压降水井设计及基坑底板稳定性分析提供有效的指导。

With the increasing depth of deep excavation,it is urgent to solve the problem of multi-layer confined groundwater in the excavation.It is significant for the excavation safety to find out the hydrogeological characteristics of rock and soil mass in the construction site and the supply relationship between different aquifers,obtain more accurate hydrogeological parameters for the prevention of water inrush,piping and other accidents in the engineering practice.A case study of a deep excavation project in Changzhou was carried out in this paper.In order to study the confined groundwater layerⅠa and layerⅠb at the bottom of excavation pit,unsteady flow pumping test of confined water of single well and group wells were carried out.Comparing the results of numerical simulation with the fitting curve obtained from actual observation,and the reliability of hydrogeological parameters obtained from pumping test was evaluated.According to the monitoring results of surface subsidence during pumping test and water level restoration,the influence of confined groundwater dewatering on surrounding environment was predicted,which provided an effective guidance for the design of pressure-relief dewatering wells and the stability analysis of pit floor.