Characterization of rock formation at Toshka fourth depression – Egypt

Abstract

ABSTRACT Recently, the Egyptian south valley has been considered as one of the most promising developments for the mega projects such as power stations, roads and bridges. Fresh water channels were extended through to transfer water from Nasser Lake to the irrigated land in the western desert in order to save the groundwater storage for the later usage. Rock formations generally represent a great challenge in civil engineering due to their wide spatial variability, whether vertically or horizontally. This paper presents the results of a geotechnical study that was carried out across the Toshka fourth depression, Egypt. The study comprises a comprehensive investigation programme in the field and complemented with laboratory testing programme to evaluate the physical and mechanical rock properties. The geotechnical investigation included executing boreholes with a depth up to 100 m; core and bulk samples were extracted and recovered. Moreover, an extensive laboratory testing programme was conducted on the samples. Additionally, Rock Mass Rating System was used to identify the rock mass properties, considering the effect of discontinuities planes, layers joint roughness conditions, slaking rate and in addition to the effect of wetting and drying on Rock Mass strength parameters. The results indicated that the geological formation generally composed of limestone intercalated with layers of silty claystone or clayey siltstone. The results of this study cover, among others, rock mass strength properties that should be considered as a design parameters or regarded as guidelines for the design of any future development in the region.