Stability Improvement Against Toppling Failure in the Upper Plateau of Gebel Mokattam

Mokattam is an urban, highly populated region in Egypt that has been subjected to many failures over the past decades, causing huge losses. Toppling failure of the upper limestone blocks in Mokattam often develops due to the differential settlement in the underlying claystone as a result of softening caused by infiltrating water through limestone joints. This mechanism leads to block inclination, increasing the tendency of overturning and sliding outside the slope. Previous research attributed the occurrence of failure to this inclination with little attention to safety factor calculation and lacked emphasis on the effect of cumulative water pressure in limestone joints. This study introduces an integrated conception of the failure mechanism in Mokattam, presenting safety factor calculations and providing a method to quantify the adverse effect of rainfall on stability against toppling, and finally introducing a stability improvement alternative. Safety factor calculations showed that limestone blocks that are stable under their weight could experience a significant reduction in the factor of safety (F.O.S) due to the cumulative water pressure and can further experience failure. Upon studying the effect of several parameters on a factor of safety, this study illustrates the significant increase in stability of blocks using rock bolts, providing a guideline that can be used for the optimum usage of rock bolts for increasing stability in similar cases.