Analysis of rockfall hazards along NH-15: A case study of Al-Hada road

Abstract

The rock instability of granodiorite mountain rock located within a key route for the Mecca city (Al Haram) and Al-Taif (tourist place) was investigated. In this study eight, highly susceptible sites from 22 km road selected for kinematic and rockfall analysis to avoid rockfall consequences. Based on the field investigation, this mountain road is characterized by nearly vertical cut slopes with highly fractured and jointed rocks leading to the occurrences of rock instability. The kinematic results indicated that planar, wedge and toppling failure is the main reason for rock block instability. Furthermore, the rockfall movement trajectory and bounce height were modeled with their corresponding translational velocity and kinetic energy for delineating the dynamics of a falling rock block. The bounce height ranged from approximately 1.3 m to > 8 m. The energies ranged from low (< 30 kJ) to high-intensity zones (> 300 kJ) capable of causing mortality and damaging infrastructure. The present study indicates the study area is at risk of rockfalls and preventive measures are required to minimize the rockfall hazard. Study results can serve as a reference for predicting rockfall areas under similar conditions.