Abstract:
The paper presents experimental observations of the anisotropic effect of dry and saturated lineated schistose rock on deformational behaviour and fracture patterns under indirect tensile loading conditions. Dry mylonitic quartz-mica schist (M-QMS) shows strength minima in between lineation orientation of 20 degrees-30 degrees with loading direction, whereas dry crenulated quartz-mica schist (C-QMS) shows strength minima in between 45 degrees and 60 degrees. Water saturation significantly reduces the failure strength and shifts the strength minima towards a higher angle. In addition, the water saturation effect induces plasticity along the lineation direction. P-wave velocity is found to be maximum along lineation direction, which continuously decreases to a minimum value across the lineation. Three types of fracture patterns, namely layer activation, central and non-central, are observed for both the rock types. For both the rock types, tensional fractures occur when the lineation is inclined at 0 degrees and 90 degrees to the loading direction, whereas shear and mixed-mode fractures occur at all other orientations. Fracture through the layer activation is prominent in saturated specimens compared to the dry specimens for beta angle range of 15 degrees-60 degrees and 15 degrees-45 degrees in the case of M-QMS and C-QMS, respectively.