基坑悬挂式止水帷幕渗流的共形映射

Conformal mapping of unclosed cut-off curtain seepage in the foundation pit

近年来,在强透水地基中建构筑物基坑日趋增多,尤其对于水头较高且强透水层较厚的情况,由于采取落地式止水帷幕成本过高,或者无法施工,这时往往采用悬挂式止水帷幕并结合坑内抽水、坑外回灌的方式,使基坑内外渗流达到平衡,从而使基坑外水位基本保持不变,而坑内水位达到要求的降深。由于悬挂式止水帷幕的存在使该类基坑渗流求解格外复杂,因而这种基坑目前尚缺乏精确的理论表达式,常常采用"大井法"来计算基坑的涌水量。本文采用共形映射方法,通过建立数学模型,推导坑底以下无相对透水层基坑涌水量表达式。

In recent years,the amount of foundation pits in highly permeable layer is increasing. The cost for completely water cut-off will be very high and sometimes it is difficult to carry out if the foundation pit excavated in highly permeable strata with high water pressure. Unclosed cut-off curtain combined with dewatering inside the pit and recharging outside is always employed to maintain the groundwater level in both sides. The seepage analysis for this situation is very complex and there is no accurate theoretical expression currently. The water discharge is usually predicted by large-diameter-well method. Based on conformal mapping,the mathematical modeling is built and the expression of seepage discharge for unclosed curtain is deduced.