Large-Scale Experimental Simulation Studies on Rainfall-Induced Landslides Using Artificial Rainfall Simulator and Its Evaluation Using Conventional- and Optical-Based Monitoring Method

In the Indian Himalayan region, landslide-induced hazards increased significantly over the past several decades, creating considerable economic losses. As per the global landslide datasheet, most landslides in the Himalayan region are rainfall-induced. In rainfall-induced landslide studies, laboratory flume tests were found more significant for understanding the slope failure mechanisms under artificial rainfall conditions. This study used a laboratory-scale flume tank with larger dimensions of 5 m x 1.5 m x 1.0 m to investigate the initiation and propagation of the landslide mechanism and to understand the possible factors involved in soil mass movements during rainfall-induced landslides. An artificial rainfall simulator arrangement was specially developed and calibrated in this study to simulate artificial rainfall conditions. For testing, debris soil collected from a landslide site at Narendra Nagar, Uttarakhand, was used. Rainfall intensity, slope angle and soil water content were selected, similar to the field conditions for flume testing. The influence of selected site parameters on the slope failure mechanism was investigated. This study also compared conventional- and optical-based 2D digital image correlation techniques (DIC) to assess the slope failure mechanism. The estimated strain increment and displacements using the DIC technique and observations on pore pressure response and moisture content variation provided detailed insights regarding the slope failure mechanism and also confirmed the application of a non-contact-based instrumentation scheme for monitoring in landslide experiments. Based on the experimental results, a rainfall intensity-duration threshold was proposed for estimating rainfall-induced slope failures.