Rock Slope Instability and Rockfall Modeling Analysis and Mitigation at Mountainous Road, Western Saudi Arabia

Construction of mountain roads at western Saudi Arabia is a challenge due to geomorphological constraints, where the rock masses are high-rising, steep slopes, and structurally complex. Al-Hada mountain road of almost 22 km long shows many incidents of rock slope instability and rockfalls. A studied 120 m long portion of a mountain road lies along a steep man-made and natural sharp slope cut suffers from slope failures and rockfall's incidents, increase mainly in rainy seasons. The rock masses are medium quality igneous rocks. The 50 m-height rock slope-cut along the road has no benches. The steep man-made rock slope cut is very close to the road with narrow ditches, form a potentially source area for rockfalls and potential hazard zone for slope failures. The Dips, Plane, Swedge and RocFall computer programs were utilized to perform modeling and mitigation on the rock slope. Input field rock masses geotechnical parameters such as: block size, seeder point's locations of blocks falls; slope angle, restitution coefficients, and slope roughness were studied, in addition to other geotechnical strength parameters measured in the laboratory. These key parameters were used to model the slope stability and rockfall's characteristics such as: bounce height, kinetic energies, and translational and rotational velocities. The program modeled the proposed location, height and energy of the rock bolts, and rockfall barriers and collectors. Modeling of the input parameters indicates the increase of the rock blocks hit energy and their end-point as the block size and restitution coefficients increases.