Rock mass classification of Eocene karstic limestone in New Galala City, Northern Galala Plateau, Gulf of Suez, Egypt

Abstract

T HE Egyptian Government is aiming to construct new urbanization development projects in order to expand beyond the old Capital; Galala city is one of the greatest new cities projects. The project location is sited on Karstic limestone that necessitates detailed and careful geological and geotechnical studies. The present research is focused on detailed field investigation, rock mass classification, evaluation of rock quality and stability for foundation of the new Galala City and the new highway crossing the karstic Lower Eocene limestone capping the Northern Galala Plateau.Detailed joint characterization is done through careful site investigations to evaluate the different parameters of discontinuities found in five stations. Rock Mass Rating (RMR) as a measure of the strength and rock mass deformation properties is determined to define the limitations in the rock mass and the unstable areas based on study of in-situ strength, groundwater condition, and joint condition measurements. Slope Mass Rating (SMR) is evaluated depending upon the RMR value added to factors including dip and dip direction of slope in relation to the different joint sets and also excavation method in the different study locations and the effect of geologic structures include fractures, joints, faults and damage zones. Kinematic analysis is performed to detect the potentiality of the different types of failure modes in the selected sites.The study specifies good (Class II) to fair (Class III) in RMR and Normal rock quality and partly stable in SMR classification for the studied locations. Kinematic analysis indicates the possibility of planar, wedge and toppling failure in most locations, however, the most critical situation is found in two location; one along the asphaltic road and the other on a NW trending scarp limiting the city location from its norther border. The first location is considered safe for wedge failure with factor of safety higher the unity under static and dynamic conditions. The second location is unsafe for wedge failure with safety factor smaller than unity even under static condition.The study indicates a good foundation for urbanizing a new city if the effect of human urban water factors on the foundation bedrock karstic limestone is taken into account. The presence of a scarp bounding the city location from its northeastern border represents a critical situation that must be taken in consideration.