Geotechnical Interattraction of Granites from Ouaddai Region (East) for Use in Civil Engineering

This study focuses on the different qualities of granitic materials in the eastern region of Chad that can be used in construction. Achklun and Amgala are located in the North and South of Abéché, region of Ouaddaï (Eastern Chad). In Achklun and Amgala crop out, granites which are cross cut by diaclases and veins. Petrographic investigation of rocks shows that granites are of two types: (1) fine grains biotite granites constituted of quartz, orthoclase, plagioclase biotite andopaque minerals and (2) coarse grains amphibole biotite-granites made up of quartz, orthoclase, plagioclase biotite amphibole and opaque minerals. Structural feature investigated are diaclases and veins. Diaclases are observed in biotite granite and amplibole biotite-granite. They display NE-SW trend direction. Veins are observed in amplibole biotite-granite. They have granitic composition and pegmatitic texture. Veins display NE-SW dominant trend direction. The NE-SW trend direction suggests that their emplacement benefited from diaclase network. Geotechnical studies indicate that fine grains biotite granite is more resistant than amphibole biotite-granite. The resistant may vary from one station to another in the same rock type. This variation is due to mineral composition grain sizes and the intensity of fractures (diaclases). Base on field observations laboratory investigation the present work permitted to select the granite more adapted for various building.