ABSTRACT
Human activities are continuously altering the steepness of natural slopes, making them vulnerable to slide under natural triggering factors like earthquakes and rainfall. Quarrying activities in particular, contribute largely to slope failures worldwide, especially when unorganized and chaotic. In Lebanon, quarries are scattered randomly across the country and lack proper urban planning and management. Regional scale maps were recently generated in a Geographic Information System (GIS) platform to identify hazard and risk levels of co-seismic and rainfall induced landslides. However, their applicability to quarried slopes was not tested. In this research, we present a methodology to assess, at a site specific level, the hazard and risk levels of quarried slopes under three conditions: dry, heavy rainfall, and seismic events. The aim is to also ascertain the degree of accuracy of the regional scale maps in predicting landslides in quarried areas. A limestone quarry in Bafliye, Southern Lebanon, was mapped with a DJI Phantom 4 V2.0 drone, recreated as a 3D scene in Pix4D Mapper, assessed kinematically in Rocscience DIPS 7.0, and analyzed using limit equilibrium and numerical modelling techniques using both Rocscience SWEDGE 7.0 and RS2 11.0. At failure, the maximum runout distance and the corresponding angle of reach were determined in Rocscience RocFall 8.0. The studied slope failed under both seismic events with 10% exceedance probability in 50 years, and rainfall events with 10-year return period. The runout distance was relatively small, yielding a low risk failure. The safety factors matched between the site specific and the regional scale analyses, while risk levels did not. This indicated that the regional scale analysis is adequate in predicting only hazard levels at quarried sites.
