Mechanical and disintegration behaviors of carbonaceous rock under drying-wetting cycles

Abstract

Effects of drying-wetting cycles and loads on the mechanical and disintegration characteristics of carbonaceous rock were investigated by triaxial compression tests and disintegration tests in this study. The disintegration phenomena of carbonaceous rock exposed to drying-wetting cycles were analyzed, and the corresponding mechanisms were discussed. The test results showed that drying-wetting cycles lead to the deterioration of particle contact conditions in carbonaceous rock, with a more pronounced impact on the elastic modulus than on the peak strength. After 20 drying-wetting cycles with a range of 5%, the elastic modulus and the peak compressive strength were reduced by 56.86% and 23.71%, respectively, as compared to those at the initial state. Confining pressure was found to mitigate this deterioration in mechanical properties. The disintegration process of carbonaceous rock was elucidated, and its underlying mechanism was revealed from an energy perspective. The mass percentages of each particle size fraction gradually stabilized after five cycles. As the number of cycles further increased, solid particles larger than 5 mm continued to disintegrate, while particles smaller than 5 mm would become increasingly difficult to break down. Particles in the 2–5 mm size range accounted for the highest mass fraction after the complete disintegration of carbonaceous rock. The dissolution of carbonate minerals and cation exchange on the surface of clay mineral particles were the main reasons for the rapid disintegration of carbonaceous rock exposed to drying-wetting cycles. It is believed that the outcomes of this study would shed light on the deterioration mechanism of mechanical properties for carbonaceous rock under adverse natural conditions.