Abstract: The pore pressure response of a two-dimensional seepage field in an isotropic soil layer under the condition of periodic fluctuation of groundwater level is studied analytically. The soil around the pit is divided into four regular regions， and the expressions of the series solution form of the pore pressure response in each region are obtained by applying the superposition principle and the method of separation of variables， and the explicit analytical solution of the pore pressure of the seepage field around the pit is solved by combining the continuous conditions between the regions. The results of the analytical solution are compared with the results of numerical software and semi-analytical solutions to verify the correctness of the analytical solution method in this paper. Based on this solution， the influence of the variation of engineering parameters such as water level inside and outside the pit on the pore pressure response distribution and phase lag is analyzed. The results show that the pore pressure response and phase lag are influenced by the engineering parameters of the pit， and the influence on the far-field pore pressure response and the phase lag inside the pit is more obvious.

Key words: separation of variable method; foundation pit seepage field; analytical solution; pore pressure response; phase lag