富水砂层水文地质参数反演及基坑降水围护优化

INVERSION OF HYDROGEOLOGICAL PARAMETERS IN WATER-RICH SAND LAYER AND OPTIMIZATION OF EXCAVATION DEWATERING AND SUPPORT SYSTEM

位于富水砂土地区的某基坑所在场地有着地下水水位高,地层中隔水层缺失的特点。在该地区进行基坑降水时,由于坑内外水力联系无法隔断,降水会对坑外环境造成持续影响,威胁基坑周边环境安全。基于在该场地进行的一系列单井和群井抽水现场试验,通过建立三维非稳定流渗流模型,借助三维数值模拟软件进行反演计算。得到了场地内各主要含水层的水平向渗透系数、竖向渗透系数、贮水率等水文地质参数;基于验证的数值模型,对比分析了不同止水结构深度在该富水砂土地区进行基坑降水时,周边环境受到的影响差异。结果表明:止水结构插入深度越大,坑外环境受到的影响越小。综合考虑基坑环境保护等级和不同方案下环境影响,得到了该场地基坑降水最优围护方案。

One excavation is located pit site in a water-rich sandy soil area,which is characterized by high groundwater level and lack of aquifer in the stratum.Due to hydraulic connections inside and outside the pit,dewatering of the foundation pit has a continuous impact outside the pit,posing a threat to the environmental safety around the foundation pit.Based on a series of single-well and multi-well pumping tests on site,a 3D unsteady flow seepage model was established,and inversion calculations were carried out with 3D numerical simulation software,to obtain hydrogeological parameters of main aquifers within the site,such as the horizontal permeability coefficient,vertical permeability coefficient and water storage rate.With the validated numerical model,a comparative analysis was conducted on differences in the impact of foundation pit dewatering on the surrounding environment at different depths of sealing in the water-rich sandy soil area.Results show that the greater the insertion depth of water stop structures,the smaller the impact on the environment outside the pit.The optimal enclosure scheme for foundation pit dewatering on the site was developed considering the environmental protection level of the foundation pit and the environmental impact of different schemes.