ASSESSMENT OF LANDSLIDE SUSCEPTIBILITY AND ROCK-SOIL SLOPE STABILITY ANALYSIS (RSSSA): USING GIS AND ROCSCIENCE (SLIDE) SOFTWARES

Abstract

A landslide is a downhill movement of rock or soil, or both, over the ground surface's crust in the form of a curved (rotational) or planar (translational) rupture. There is still a lack of realistic policies for landslide risk management due to a lack of (rare) landslide assessment, knowledge of various causative factors, triggering factors, methods of counting, measuring, analysis, and landslide susceptibility mapping practices. Two of the most common approaches to landslide mapping are field surveys and visual analysis of stereoscopic aerial imagery. These procedures, on the other hand, not only take a long time, but are costly, labor-intensive, and physically exhausting operations in a large area. Therefore, to overcome this problem, it is better to use remote sensing software to save time and money for survey data collection processes and omit errors due to landslide assessments, like during counting, measuring the area or size and analysis of landslides, estimation of the time it occurred. The objective of this research was to study different causative and triggering factors, evaluate frequently experienced landslides/slope failure points and prepare a landslide hazard zone map for the entire study area using a bivariate statistical and numerical approach. For this study, removed/lost surfaces along the Zabidar Mountain road corridor were extracted by the cut/fill spatial analyst tool in GIS and their frequency ratio was evaluated for the past six consecutive years. The landslide hazard zone map was created on the Arch map using a customized raster calculation to identify regions vulnerable to landslides/slope stability failure. According to the landslide hazard map, 27% (4.8 km2) of the area is free from the landslide zone, 29% (5.2 km2) is susceptible to the landslide zone, 23% (4.1 km2) is low to the landslide zone, and 21% (3.8 km2) is truly dangerous to the landslide zone. Based on the hazard map created, geotechnical characterization of selected points was studied by conducting sieve analysis, angle of repose, unconfined compressive strength and direct shear tests. Rocscience software (Slide) was applied for the limit ,equilibrium method analysis of weathered rock mass along the road corridor for cross check of the landslide hazard zone map. The result shows, 80% are unstable (factor of safety less than 1.5). In this study, it was also identified that 588 households are in the no-landslide danger zone, 555 households are living in the medium to landslide danger zone, 228 households are living in the low-risk landslide zone, and 61 households are living in the high-risk landslide zone. The findings of this study might be useful to guide a suitable method for survey data collection and its analysis, for decision-makers in future land management, hazard mitigation operations, selecting appropriate sites for infrastructure developments, flood control systems, and drainage canals