Study on Early Warning of Landslides by Using Rainfall Parameters

　　Many factors can trigger slope failure, with rainfall and groundwater variation being the primary causes. The failure time of rainfall-induced slope failure may be affected by the depths of the sliding surface and rainfall types, including rainfall patterns, duration, and the return period. Hourly accumulated rainfall may not be an efficient parameter for predicting slope failure, considering rainfall type variations or sliding surface depths. This study examines the appropriate rainfall parameters and thresholds for predicting slope failure with shallow and deep sliding surfaces at 10m and 40m depths.

　　This study adopted PLAXIS LE 3D, the limit equilibrium method, to obtain the factor of safety variation by time under different rainfall patterns, return periods, and durations. By accumulating rainfall over various periods, we derived various rainfall curves, referred to as” rainfall parameter curves” in this study. Using the rainfall parameter curves and the factor of safety variation, we can find the suitable rainfall parameters for shallow or deep sliding surfaces and then obtain corresponding rainfall thresholds for early warning. The result showed that short-term rainfall parameters and small threshold values are more appropriate for alarming slope failure with shallow sliding surfaces. On the other hand, long-term rainfall parameters and large threshold values are more appropriate for alarming slope failure with deep sliding surfaces. The rainfall parameters and the threshold values have a stronger relationship with the depths of sliding surfaces than with the types of rainfall.