Stability and time-delay effect of rainfall-induced landslide considering air entrapment

Abstract

The pore air pressure of the soil layer has an obstructive effect on the infiltration of the rainfall-induced landslide. Therefore, the hydraulic hysteresis caused by air entrapment in the infiltration process of the slope also reduces the anti-sliding force of the slope. A method considered the air entrapment of the closed gas in soil particles’ pores is developed to study the time-delay effect and slope stability during rainfall. The Green–Ampt infiltration model is used to obtain the explicit analytical solution of the slope infiltration considering air entrapment. Moreover, the relationship between the safety factor, the rainfall duration, and the depth of the wetting front under the three rainfall conditions (qrain = 10, 26, 51 mm/h) is discussed. The results show that the air entrapment causes a significant time-delay effect of the landslide, and the hydraulic hysteresis is the strongest under the condition of heavy rainfall (qrain = 51 mm/h). The air-entrapment will have a supporting effect on the wetting front and reduce the slope normal stress. In infinite slope cases, the air entrapment under violent rainfall (qrain = 51 mm/h) will greatly reduce the slope safety factor.