Passive Earth Pressure Calculation Considering Composite Failure Surface and Anisotropic Seepage

Extreme environmental conditions, such as heavy rainstorms and urban waterlogging, can cause seepage within backfill, significantly reducing the passive earth pressure on retaining structures and compromising their stability. To study the earth pressure under the influence of seepage, a modified calculation method of the passive earth pressure of retaining structure considering the anisotropic seepage effect is proposed in this paper. The effective soil reaction distribution on the sliding surface was obtained by solving the modified K9tter equation, and the pore water pressure in the soil behind the wall was calculated by using the two-dimensional Laplace equation. Then the passive soil pressure coefficient of the retaining structure was calculated by an iterative trial and error method. This method obtains the position of passive earth pressure through moment balance, and can analyze the main controlling factors affecting the magnitude and distribution of passive earth pressure. The results show that the degree of seepage anisotropy has a significant effect on the magnitude and distribution of passive earth pressure. The passive earth pressure decreases with the increase of the anisotropy coefficient, and the maximum decrease can reach 20%. The increase of the effective internal friction angle and the decrease of the anisotropy coefficient will cause the decrease of the combined action position of passive earth pressure. Its action position will fluctuate within the range of 2/5 to 1/10 of the wall height.