落底式止水帷幕条件下承压含水层水文地质参数计算方法研究

Calculation methods for hydrogeological parameters of confined aquifers under the condition of drop waterproof curtain

落底式止水帷幕在具有典型二元结构地层的武汉地区深基坑工程中被广泛应用,而落底式止水帷幕的存在改变了二元结构含水层中地下水的渗流环境,为此提出了落底式止水帷幕条件下承压含水层水文地质参数的解析和数值计算方法,并结合武汉园林路地铁站深基坑现场抽水连通试验数据验证方法的正确性和可靠性。结果表明:根据新建立的考虑落底式止水帷幕条件下的解析法公式计算得出承压含水层的渗透系数为17.47~25.55 m/d,平均值为20.722m/d,而通过三维数值模拟反演得到承压含水层的水平向渗透系数(粉细砂层为21.6m/d,细砂层为25.92m/d)和垂向渗透系数(粉细砂层为2.592m/d,细砂层为3.456m/d)具有明显的各向异性,新提出的解析法和数值法均能得到可靠的承压含水层水文地质参数,可为落底式止水帷幕条件下基坑降水设计提供更直接的科学依据,具有一定的推广和应用价值。

The drop waterproof curtain is widely used in deep foundation pit engineering in Wuhan area with typical dual structure strata,and the existence of the drop waterproof curtain changes the seepage environment of groundwater in the dual structure aquifer.Therefore,the analysis and numerical calculation method of hydrogeological parameters of confined aquifer under the condition of the drop waterproof curtain are proposed.The correctness and reliability of the method were verified by the test data of deep foundation pit pumping in Wuhan Garden Road subway station.The results are as follows:the permeability coefficient of confined aquifer is calculated from 17.47 to 25.55 m/d with an average value of 20.722 m/d by the newly established analytical formula considering the drop waterproof curtain.The horizontal permeability coefficient of confined aquifer is obtained by three-dimensional numerical simulation inversion(21.6 m/d for the silty sand layer and 25.92 m/d for the fine sand layer)and the vertical permeability coefficient(2.592 m/d for the fine sand layer and 3.456 m/d for the fine sand layer)has obvious anisotropy.The newly proposed analytical method and numerical method can obtain reliable hydrogeological parameters of confined aquifer.It can provide a more direct scientific basis for the design of foundation pit dewatering under the condition of the drop waterproof curtain,and has a certain popularization and application value.