ANISOTROPIC BEHAVIOR AND MECHANISM OF DRY AND WATER-BEARING SCHIST IN TERMS OF CHARACTERISTIC STRENGTH AND ENERGY EVOLUTION

In this study,the quartz mica schist was taken as the tested object. The uniaxial compression test was used to explore the influence of loading direction on the characteristic strength and energy evolution of this brittle schistose rock under dry and water-bearing conditions. Combined with the characteristics of micro fabric and macro failure mode,the mechanism of mechanical anisotropic behavior of schist was revealed. Results show the following. (1)During the loading process,the energy evolution curves of rocks have a good corresponding relationship with the deformation damage changes. Based on this,the characteristic strengths of rocks can be determined quickly and accurately. (2)The characteristic strengths of schist in both dry and water-bearing states always follow α=90°>α=0°>α=30°. At α=30°,the schist has a more sensitive response to water with respect to the characteristic strength. Water enhances the strength anisotropy of schist to a certain extent. (3)At α=90°,the energy storage and dissipation of schist are always higher than those at α=0° and 30°.The tendency of rock burst of schist with α=30° is stronger than that with α=90°.The damage of rock has a relatively rapid development at α=30°. (4)The flaky minerals and micro-cracks in schist provide the material basis for water effects such as lubrication,softening and water wedge.The dominant water action varies with the loading direction. (5)The quartz mica schist has the microscopic characteristics of orientation arrangement of flake minerals and the interlayered distribution of soft and hard layers. This typical structure determines the effect of loading direction on the mechanism of cracks generation and propagation,and essentially controls the anisotropy of strength and energy of the rock.