Analytical solution of infiltration into single-layer cover under heavy rainfall events and its application for stability analysis

In recent years, extreme rainfall events have occurred frequently in China, and so investigating the infiltration law and slope stability of single-layer soil cover under heavy rainfall events is of great significance. An analytical solution for rainwater infiltration into the single-layer soil cover is presented based on the two-dimensional governing equation for unsaturated flows. This analytical solution was obtained by employing constant flow rate and constant pore water pressure head as the top boundary conditions of the cover before and after the surface soil reached saturated during a heavy rainfall event. The analytical solution was validated by comparing with the numerical results of the finite element software Geostudio-seep/W. Based on the analytical solution and the theory of shear strength of unsaturated soil, the variation of the stability safety factor of a single-layer soil cover under a heavy rainfall event was analyzed. The results indicated that the greater depth of the potential sliding surface, the slower the response of the stability safety factor to rainfall. During the whole rainfall period, the stability safety factor with the bottom surface of the cover as the sliding surface remained the smallest, indicating that the cover is most prone to sliding along this sliding surface. The analytical solution obtained in this study provides a simple and practical tool for evaluating the anti-seepage performance and stability analysis of single-layer soil covers.