二元地基基坑抽水试验及数值分析

Pumping Test and Numerical Analysis for Foundation Pit of Two-layer Foundation

秦淮河船闸地基土呈典型的二元结构地基形式,由于地质勘察阶段试验井位置选取、已有渗流通道以及影响半径取值等影响因素的存在使得地质勘查阶段渗透系数的计算值与以往的工程实践经验数值差距较大,为了更加准确的描述现场的水文地质条件,为工程降水设计、施工提供准确的水文地质参数,利用抽水试验得到的数据,对现场的地基土建立空间轴对称模型,根据建立的地基土层观测井模型以及远端孔压计所测得的水位对模型扩大分析,反算了地基土的渗透系数,一定程度上降低了影响半径以及经验公式中假设带来的一些误差以及现场基坑范围内管涌通道的影响,通过对比得到地基土的渗透系数都小于地质勘察阶段所得到的渗透系数更加接近工程实践经验数值,对基坑的涌水量进行了更加准确的定量,对工程实践有一定的指导意义。

The foundation soil form in Qinhuai River’s lock area is the typical two-layer structure .As the pilot well loca-tion selection ,existed seepage channels ,as well as radius value selection and other factors make the calculated value of permeability coefficient in geological exploration stage having larger gap compared with the empirical value in past engi-neering practices ,for a more accurate description of the hydrogeologic conditions in site so as to provide accurate hydroge-ological parameters for precipitation design and construction ,the pumping test data is used to establish the space axisym-metric model for the foundation soil in site ,and by using the established foundation soil’s observation well model and the water level from remote bore-pressure meter for the expansion analysis of the model ,the reverse calculation is made for the soil’s permeability coefficient ,so to a certain extent ,some errors from the influencing radius and empirical fomula as well as the effect of the piping channel within the scope of on-site excavation are reduced .The subsoil’s permeability co-efficient obtained by comparing is less than that obtained in the geological exploration stage ,and closer to the empirical value from engineering practices ,thus the pit’s water out flow is made for a more accurate quantification ,which could provide a certain guiding significance for engineering practices .