Degradation law and mechanism of the compressive strength of mica quartz schist under dry-wet cycles

Abstract

Objective The dry-wet cycles can promote the deterioration of the mechanical properties and stability of schist slope rock masses and induce geological disasters such as landslides and collapses. Methods Taking mica quartz schist, which is widely distributed in Shiyan, Hubei Province, as the research object, uniaxial compression tests and electron microscope scanning were carried out on mica quartz schist samples under different dry-wet cycles to reveal the degradation law and mechanism of its compressive property. Results The results show that under the action of dry-wet cycles, the degradation effect of the compressive strength and elastic modulus of mica quartz schist were obvious. The degradation rate was fast and the degradation range was large in the early stage, but the degradation rate was slow and the degradation range was low in the later stage. The macroscopic failure modes were gradually controlled by the schistosity planes, which gradually evolved from styles of "X" and "Y" failure to along the schistosity planes failure. The microstructure was characterized by continuous spalling and granulation of flake mineral particles, and the microcracks as well as pores were gradually developed, expanded and connected. The mica quartz schist produces secondary minerals, ions and rock cuttings and leaves the rock continuously under dry-wet cycles, which promotes the preferential expansion and cracking of schistosity, microcracks and other structural planes. which then degrades the overall mechanical properties of the mica quartz schist. Conclusion The research results can provide a theoretical basis for the stability analysis and treatment design of schist slopes.

Keywords

• mica quartz schist
• dry-wet cycle
• uniaxial compression test
• scanning electron microscope
• degradation mechanism
• compressive strength