Influence of Rainfall Intensity and Its Pattern on the Stability of Unsaturated Soil Slope

Rainfall infiltration is an important factor that leads to slope instability. In this study, a numerical model for slope is built to investigate the effects of rainfall intensity and its pattern on slope stability. Results show that rainfall intensity and its pattern significantly influence slope stability due the following instances: (1) the safety factor of slope initially decreases and then stabilizes during rainfall, which is defined as the effective rainfall days; moreover, when the rainfall intensity is less than the saturated permeability coefficient of soil, the effective rainfall days decreases with the increase of rainfall intensity. (2) Under the same rainfall intensity, the ultimate safety factor of sand slope when the effective rainfall days is reached is greater than that of the clay slope. (3) When the rainfall intensity is less than the saturated permeability coefficient of soil with the same total precipitation, a longer rainfall duration indicates a larger slope safety factor; conversely, when the rainfall intensity is greater than the saturated permeability coefficient of soil, a longer rainfall duration indicates a smaller slope safety factor.