Abstract: The two-dimensional steady-state seepage field of the foundation pit under suspended waterproof curtains support considering the phreatic surface is studied analytically, and an analytical method for solving the phreatic surface is given. According to the symmetry, the half section of the foundation pit is taken, and it is divided into three regular regions based on the continuity conditions of the boundary. The variable separation method is used to express the water head distribution in the three regions as a series solution. The explicit solution of the seepage field in each region is obtained by combining the continuity conditions between regions and the orthogonality conditions of the series. The water table is determined based on the condition that the total water head satisfied by the water table is equal to the position water head. The analytical solution in this paper is compared with the results of laboratory tests and finite element analysis, the results verify the correctness of the analytical solution, which has higher efficient computational efficiency than that of the finite element numerical method. Performing a parametric analysis of the phreatic surface location, it was found that the insertion depth of waterproof curtain, the width and depth of foundation pit have a non-negligible effect on the phreatic surface location. As the thickness of the cross section increases, the position of the phreatic surface gradually decreases, and the distance from the bottom of the curtain to the top surface of the confining stratum has a linear relationship with the position of the phreatic surface on the waterproof curtain, without considering the extreme conditions. As the size of the foundation pit increases, the location of the phreatic surface shows a downward trend. The influence of the inner half width of the foundation pit on the phreatic surface is significantly smaller than that of the distance from the bottom of the curtain to the top surface of the confining stratum, this influence decreases with increasing the inner half width. The location of the phreatic surface decreases as the depth of the foundation pit increases, and the depth of the foundation pit has a relatively large influence on the location of the phreatic surface.

Key words: foundation pit, waterproof curtain, phreatic surface, two-dimensional steady-state seepage, analytical solution, seepage