Models and influencing factors of the delay phenomenon for rainfall on slope stability

Abstract

The effect of rainfall on the slope may continue and the most unstable state may occur after the rainfall has stopped. This phenomenon can be described as the delay phenomenon. This paper reports on the models and influencing factors of the delay phenomenon using numerical methods. Two representative models of landslides occurring after rainfall were set up to illustrate the mechanisms of the delay phenomenon. Parametric studies were made to quantify the impact of soil types, the depth of initial water table, anisotropic conductivity, rainfall intensity and rainfall pattern on the delay phenomenon. The results indicated that slope soils with slightly smaller water-entry value and slower permeation rate of rainwater have a higher probability of generating the delay phenomenon. The most noticeable delay phenomenon was observed when the anisotropy ratio k_y/k_x = 0.5 and the saturated hydraulic conductivity of soil have similar value with rainfall intensity. Besides, the delay phenomena were the most likely to occur when rainfall intensity peak was near to the time when rainfall stopped.

Keywords:

• slope
• rainfall
• delay phenomenon
• influencing factor
• factor of safety
• landslide mechanism