考虑围护结构隔水作用的基坑涌水量计算

Calculation of Water Inflow of Foundation Pits Considering Water Insulation Effect of Retaining Structures

为解决由于地铁基坑地下水的渗流路径和面积发生改变进而导致常规计算方法得出的坑内降水与实际存在较大的差别,通过对有围护结构隔水的基坑基本渗流场流网分布特征进行研究,提出改进的基坑涌水量计算公式,并以工程实例对改进公式进行验证分析。研究结果表明:1)可将基坑周围渗流场流网分布图看成是沿围护结构中心轴线剖开的2个流网图,且两者可单独进行涌水量计算;2)基坑坑内、坑外渗流场涌水量可分别采用达西渗流定律、潜水非完整井涌水量公式计算;3)根据基坑降深与水头、降水影响范围以及坑内、坑外涌水量的函数关系,可求得基坑外的最大水位降深;4)将本文推导公式运用在实际工程计算中,结果表明改进公式能够适用于有围护结构隔水的基坑降水计算。

There are great difference between the calculated de-watering conditions and the actual de-watering condi-tions, due to the change in th.e seepage path and seepage area of groundwater of foundation pits. In the paper, the char-acteristics of the distribution of the flow net of the basic seepage field of foundation pits with water-proofing retaining structures are studied, optimized calculation formula for water inflow of foundation pits is proposed and verified in engi-neering cases. The study results show that ： 1 ） The distribution map of the flow net of the seepage field around founda-tion pits can be regarded as two flow net maps cut along the central axis of the retaining structure, and the two flow nets can be used to calculate the water inflow independently. 2） The water inflow of the seepage field inside the foundation pit can be calculated by Darcy law, while that outside the foundation pit can be calculated by the water inflow formula for partially penetrated well. 3 ） The maximum water level drawdown outside the foundation pit can be obtained accord-ing to the functional relationship among foundation pit drawdown, water head, de-watering influence scope and water in- flow inside and outside the foundation pit. 4） The optimized formula has been used in the de-watering calculation of ac-tual projects, which demonstrates that the optimized formula can be used in the de-watering calculation of foundation pits with retainin~ structures.