Geotechnical Evaluation of Rock Slopes of the Ain Tobi Member Using the Rock Mass Rating System, Al-Qawasim, NW Libya

Abstract

The stability of rock slopes is a major geotechnical concern, particularly in mountainous regions where discontinuities strongly influence slope behavior. This study presents a quantitative geotechnical evaluation of the Ain Tobi Member of the Sid As Sid Formation along the old Abughaylan mountain road, northwestern Libya, using the Rock Mass Rating (RMR) system. Field investigations included lithology, discontinuity characteristics, Rock Quality Designation (RQD), intact rock strength, and groundwater conditions. The upper dolomite slopes achieved an RMRbasic value of 67, corresponding to Good Rock (Class II), whereas the lower limestone slopes yielded values of 42–45, corresponding to Fair Rock (Class III). The results demonstrate that the RMR system provides a reliable and practical approach for evaluating rock mass quality and supporting geotechnical assessment and engineering decision-making in the study area. Future studies are recommended to incorporate the Slope Mass Rating (SMR) system to provide a more comprehensive evaluation of rock slope stability by considering the relationship between discontinuity orientation and slope geometry.