Stability of Rock Slopes along Raidah Escarpment Road, Asir Area, Kingdom of Saudi Arabia

The Raidah Escarpment road is located north west of Abha city, Asir region, Kingdom of Saudi Arabia. This escarpment road represents an important corridor in the area which connects different villages and tourist resorts with each other. The total length of this road section is about 9 km which passes through a highly mountainous area. The road also passes through areas of different geological hazards (rock, debris flow, soil, and weathered zones). The different environmental factors (e.g. intensive rainy summer), variable geological and structural elements (weak rocks, slide debris weak soils, shear zones, and faults) difficult road characteristics (narrow roads with tight horizontal andvertical curvature) and various human activities in the area make the road susceptible to frequent slope failures (rockfalls, rock sliding, debris flow, soil slides, and raveling) from time to time. This paper deals with the evaluation of the stability of the rock cuts along the Raidah escarpment road using two methods including a structural controlled method and a raveling type method.

Raidah escarpment rock cuts have been classified into sixty nine stations which were investigated and subsequently rated. Results of this study indicated that: (1) Based on the structiural control mode of failures, it was found that 12 stations are potentially unstable due to planar, wedge, and toppling failures, and out of them five stations have a major impact on the road in the event of failure, including stations 11, 17, 20, 31, and 40. (2) According to the Modified Colorado Rockfall hazard rating system, it was found that 13, 12, 13, 17, and 49 stations are of high, high to moderate, moderate, moderate to low, and low hazard. On the other hand, it was found that 13, 11, 11, and 69 stations have a high, high to moderate, moderate, and low impact on the road in the case of failure. (3) According to the field simulation tests it was found that 6 stations potentially show highly problems from rolling and bouncing rocks. However, out of these sites it was found that only 4 stations have a high impact on the road due to rolling and bouncing. (4) the areas that are impacted by the debris flows have been mapped and determined. Finally, different recommendations and remediation methods have been discussed to minimise the impact of problimatic sites.