New Approach of Geomechanical Properties by Scale Effect and Fractal Analysis in the Kedougou-Kenieba Inlier (Senegal-West Africa)

Abstract

This paper shows geometric aspects of rock masses in the Senegalese side of Kédougou-Kéniéba inlier. The studies are done in one part on sedimentary rocks (represented by sandstones) with stratification and on the other part in igneous rocks (represented by basalts). Geometric studies are the fractal configuration and the scale effect. Scale effect is stud - ied by comparing the results of mechanical tests done in the laboratory and on outcrops. For all samples, laboratory pa - rameters are highe r than values of field. In this paper, scale effect is characterized by the decreas e of mechanical pa - rameters from laboratory samples to field. The scale coefficient is defined and characterizes the relation between me - chanical properties. More important ly, the scale effect is more significant . This scale effect depends largely on the rock anisotropy. The anisotropy depends on the fracturation and the filling. The scale effect take s into account the fracturation, the filling minerals and their diversity which define the complexity of the rock. The anisotropy is complex; the impact of scale effect traduced by an increase of scale coefficient is the highest . Configuration of discontinuities also defines fractal geometry. This fractal aspect appears on the asperities, the spacing and the apertures of discontinuities. The fractal dimension is different from a parameter to another. All these two parameters estimate the stage of fracturation of the rock in a geological system and depend one on another if they are studied in the same element.