Infiltration, runoff, and slope stability behaviors of infinite slope with macropores based on an improved Green-Ampt model

Infiltration-runoff-slope instability mechanism of macropore slope under heavy rainfall is unclear. This paper studied its instability mechanism with an improved Green-Ampt (GA) model considering the dual-porosity (i.e., matrix and macropore) and ponding condition, and proposed the infiltration equations, infiltration-runoff coupled model, and safety factor calculation method. Results show that the infiltration processes of macropore slope can be divided into three stages, and the proposed model is rational by a comparative analysis. The wetting front depth of the traditional unsaturated slope is 17.2% larger than that of the macropore slope in the early rainfall stage and 27% smaller than that of the macropore slope in the late rainfall stage. Then, macropores benefit the slope stability in the early rainfall but not in the latter. Macropore flow does not occur initially but becomes pronounced with increasing rainfall duration. The equal depth of the wetting front in the two domains is regarded as the onset criteria of macropore flow. Parameter analysis shows that macropore flow is delayed by increasing proportion of macropore domain ( ω f ), whereas promoted by increasing ratio of saturated permeability coefficients between the two domains ( μ ). The increasing trend of ponding depth is sharp at first and then grows slowly. Finally, when rainfall duration is less than 3 h, ω f and μ have no significant effect on the safety factor, whereas it decreases with increasing ω f and increases with increasing μ under longer duration (≥ 3 h). With the increase of ω f , the slope maximum instability time advances by 10.5 h, and with the increase of μ , the slope maximum instability time delays by 3.1 h.