Comparative Analysis of Fracture Characteristics and Mechanical Properties of Shale and Slate Based on Triaxial Compression Test

In this paper, to study the failure characteristics and mechanical properties of slate and shale, the authors have conducted triaxial tests on shale and slate samples. To evaluate the peak stress and the destruction mode in the samples, the tests are performed on a triaxial rock-mechanical testing system. The experimental results show that compression would cause multiple cracks in shale. The cracks are characterized by a small width, and none of them are through cracks. When a slate sample is subjected to compressive failure, the developed cracks are characterized by a comparatively large opening, and some cracks are through. The compressive strength of shale is three times higher than the compressive strength of slate, and the Poisson’s ratio of shale is lower than that of slate. In the process of compressive failure of shale, the deformation is small, and the strain increases linearly along the direction of the principal stress. In the process of deformation of slate, the deformation is great, and the strain increase is divided into two stages – fast increase and slow increase. Comparison of mechanical properties of these types of rock with different lithology can provide important background for shale gas reservoir fracturing and slate foundation consolidation.