Analytical solution for rainwater infiltration in monolithic soil covers under heavy rainfall and its implications for practice

Global warming has caused frequent occurrences of extreme rainfall events worldwide. Studying the rainwater infiltration in monolithic soil covers (MSCs) and associated slope stability under heavy rainfall presents practical significance for landfill management. This study established an analytical solution for rainwater infiltration in MSCs during heavy rainfall assuming that the soil hydraulic properties follow exponential forms. The analytical solution was used to calculate the factor of safety (FOS) of MSCs after the verification with numerical simulations. It is found that the FOS for the potential slip surface at the cover bottom remained the lowest during and after heavy rainfall. The percolation and FOS might present pronounced “lag effects”, meaning that the maximum percolation rate and minimum FOS occurred after heavy rainfall. A parametric study was conducted to reveal the influencing factors on the hydraulic response and slope stability of MSCs based on the analytical solution. Relevant results demonstrate that the hydraulic performance and slope stability could be improved by decreasing soil saturated hydraulic conductivity, increasing soil desaturation coefficient, and lowering water level in landfills. The results also reveal the existence of a threshold of soil saturated hydraulic conductivity (1 × 10 −8 m/s for this study) for controlling the hydraulic performance and slope stability of MSCs. Furthermore, the analytical solution was applied to determine the rainfall intensity–duration threshold curves of MSCs. The results indicate that the obtained curves of MSCs satisfied exponential forms. This study provides an effective tool and valuable guidance for the design and maintenance of MSCs.