Response characteristics and mechanism of the strength and energy of schist to the schistosity orientation and water

In this study, uniaxial compression testing was carried out to investigate the response of quartz mica schist to water in terms of strength and energy anisotropy. The micromechanism and water action mechanism of the anisotropic properties of the schist were further discussed based on microscopic observations of the rock fabric and analysis of the mineral composition of the solid precipitant after immersion. Mechanical tests reveal that both the failure strength and crack initiation strength of dry schist change in a U shape with the schistose angle; moreover, the strength anisotropy of schist generally increases with increasing immersion time. The specimen with α = 30° has the minimum energies, while that with α = 90° exhibits the maximum total and elastic energies. The total and elastic energies of dry specimens decrease significantly after saturation, but the influence degree of water on the energy of schist differs with the schistosity orientation. The energy response of specimens with α = 30° and 0° to water is more sensitive than that with α = 90°. The internal energy allocation of schist was found to be associated with the schistosity orientation and immersion time. Based on the analysis of microcrack propagation and macro-failure, it is concluded that the fabric of schist plays an essential controlling role in the strength and energy anisotropy. The response of anisotropy to water is closely dependent on the lubrication and disintegration of flaky minerals and the hydraulic action on the tips of voids in response to external compression.