Slope Stability Analysis in Transient Rainfall Conditions

Rainfall-induced slope failure is a common geotechnical problem, particularly along newly excavated highway cut slopes. For designing the optimum stabilization solution for such excavated slopes, the investigation of slope behavior under rainfall conditions is essential. The present study deals with the instability problem of an under-construction highway cut slope along NH-31 in Koderma area, Jharkhand, India, under antecedent rainfall conditions. The studied hill section is being excavated for highway expansion near Tilaiya Reservoir. The studied slope is characterized by high to moderately weathered mica schist rock overlain by 1–5 m cover of residual soil with debris. To predict the reactivation of the existing highway section in response to antecedent rainfall, initially, the maximum rainfall in 1 day is examined, considering the specific failure event. Then, the numerical stability analysis has been carried out under varying rainfall conditions using the limit equilibrium method based on SLOPE/W and the finite element method based on SEEP/W and Phase 2. Additionally, the instability mechanism and associated factor of safety of the slope have been investigated with independent variable, such as rainfall intensity. The study signifies the role of rainfall characteristics in designing the optimum stabilization measures for the engineered slopes characterized by residual soil cover.