Evaluation of geotechnical properties of Cretaceous sandstone, Western Desert, Egypt
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ORIGINAL PAPER
Evaluation of geotechnical properties of Cretaceous sandstone, Western Desert, Egypt El-Sayed Sedek Abu Seif 1,2
Received: 5 March 2015 / Accepted: 11 January 2016 # Saudi Society for Geosciences 2016
Abstract The Western Desert, Egypt, mostly covered by clastic sedimentary rocks ranging in age from Lower Cretaceous to the Quaternary. Taref Formation of Nubian Group constitutes one of Cretaceous succession; it consists mainly of yellowish, pale red, pink, and white massive and cross-bedded sandstone in fining-upward cyclic manner. The petrographical parameters and mechanical properties of these clastic rocks must be integrated to better understand their geotechnical behavior. Mineralogically, it composes quartz, feldspars, and rock fragments, with an average value of 97.9, 1.2, and 0.9 %, respectively. Accordingly, Taref Sandstone can be classified as quartz arenite. The roundness of grains are dominated by sub-angular, sub-rounded, angular, rounded, very angular, and well rounded with an average value of 36, 25, 17, 9, 7, and 6 %. Its dry density (γd, g/cm3) varies from 1.65 to 1.87 g/cm3 that indicates Taref Sandstone classified as dense-very dense sandstone. Porosity (n%) ranges from 9.41 to 13.59 % that means that it ranges from medium to high porous sandstone. The dry uniaxial unconfined compressive strength (UCSdry) and point load strength index (IS50) values indicated that its compressive strength rages from moderately strength to very high strength and both of them are closely related. The porosity (n%) of Taref Sandstone has a significant correlation with mostly its physical and mechanical properties of the studied sandstone. Through matching correlation data among these parameters, it was clearly indicated that both
* El-Sayed Sedek Abu Seif [email protected]; [email protected]
1
Faculty of Earth Sciences, King Abdul Aziz University, Jeddah, Saudi Arabia
2
Geology Department, Faculty of Science, Sohag University, P.O. Box.82524, Sohag, Egypt
porosity (n%) and dry density (γd) had been considered as the major parameters influencing other physical and mechanical properties of the studied Cretaceous sandstone samples. Keywords Taref Formation . Mineralogy . Dry density . Porosity . Rock strength
Introduction In southern Egypt especially in Western Desert, most of the rocks are clastic sedimentary rocks ranging in age from Lower Cretaceous to the Quaternary, including sandstone, shale, and mudstone, where the sandstone of Taref Formation was considered as the most famous and widely distributed sandstone as surface and subsurface with a considerable thickness. Nearly, all buildings in Kharga City were founded on clastic sedimentary sequence of Cretaceous sequence, its area increased during the last decades owing to the migration of people from the Nile Valley and Delta regions to cover most of the low-lying areas surrounding the old city. Integrated sedimentological and mineralogical information of these sedimentary rocks improved understanding of their geomechanical properties. T
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