V. Global Stone Congress, Antalya, Turkey, 22 - 25 October 2014, pp.132
The geomechanical properties of sedimentary rocks subjected to surface and subsurface engineering applications encounter substantial variations even in very close distances. The constituents of sedimentary rocks (e.g. origin of grains and matrix type) and basic features of these constituents (e.g. grain size, shapes etc.) vary due to the formation of these rock. Consequently these heterogeneities effect the geomechanical behavior of sedimentary rocks.
In this study the change of geomechanical properties of some sedimentary rocks selected from Istanbul are investigated from the view of mineralogic, petrographic and microstructural aspects. The investigation was initiated by determining the peak strength and crack initiation threshold of samples during unconfined compressive stresses. Additionally the deformation characteristics (e.g. young modulus and Poisson ratios) were determined. Mineralogical analysis including X-Ray Diffraction (XRD) was established. Micro-textural variations were investigated on thin sections of each tested specimen before and after mechanical perturbation. During thin section studies the orientation and distribution of micro- and macro-cracks were analyzed. The grain sizes, grain-matrix ratio and spatial distribution of these constituents which forms the rock specimen were encountered. The synthesis of mechanical test results, mineralogical and detailed petrographic data revealed that the peak strength, crack initiation and elastic constants are strongly influenced by heterogeneous micro fabric of the specimen. Especially the existence of graphite veins make substantial changes in UCS, CI and elastic constants.