河岸基坑降水非饱和渗流三维数值模拟研究

Three-dimensional numerical simulation of unsaturated seepage flow in dewatering of riverbank foundation pit

本文以孔隙介质非饱和渗流Richards方程为基础,建立了可求解地下水自由面和溢出点空间位置的基坑场地三维非饱和渗流模型。通过砂土土柱渗透试验数据,验证了非饱和渗流模型混合边界条件的有效性和准确性。以常州某水利工程河岸基坑场地为例,利用所建立的三维非饱和渗流模型,对降水井失效条件下,河岸基坑的渗流场、地下水自由面和溢出点空间位置进行了预测。研究结果显示:自然条件下,在围堰、截渗墙以及降水井的共同作用下,可有效降低基坑内地下水位,但仍有部分位置存在渗漏风险;当降水井失效时,基坑底部渗漏区域面积明显增大,基坑面临浸没风险。施工过程中应重点关注基坑底部降水井是否完好有效,同时建议在4#围堰坡脚处增设降水井。

Based on Richards Equation of saturated-unsaturated seepage in porous media, a three-dimensional saturated-unsaturated seepage model for foundation pit site is established, which can solve the spatial location of free surface and overflow point of groundwater. Taking a riverbank foundation pit site of a water conservancy project in Changzhou as an example, the potential seepage field of riverbank foundation pit dewatering under the condition of dewatering well failure is analyzed by using this model. The results show that under natural conditions, the combined action of the cofferdam, seepage cutoff wall and dewatering well can effectively reduce the underground water level in the foundation pit, but there are still leakage risks in some locations. When the dewatering well fails, the seepage area in the foundation pit increases obviously, and the foundation pit is faced with the risk of immersion. In the construction process, the attention should be paid to whether the dewatering well at the bottom of the foundation pit is intact and effective. At the same time, it is suggested to add dewatering well at the slope foot of 4# cofferdam.