Evolution of Mechanical Properties of Dolomite under Coupled Dry-Wet and Cyclic Loads

Regarding the influence of cyclic loading and dry-wet cycling coupling effects on the evolution of mechanical properties of dolomite, triaxial compression tests are conducted under different dry-wet cycle counts and cyclic loading upper limits. Combined with macro-and microstructural analysis, the strength degradation, deformation characteristics, and damage evolution mechanisms of dolomite are systematically investigated. The results indicate that: As the number of dry-wet cycles increases, the mass of dolomite decreases, while the water content shows a logarithmic increasing trend. With the increase in dry-wet cycles, the peak compressive strength and elastic modulus of dolomite gradually decrease, and the damage factor exhibits a logarithmic increase. Different upper-limit cyclic loadings have a certain promoting effect on the dry-wet degradation. The elastic modulus of the specimens shows varying trends with the increase in the upper limit of cyclic loading. Dry-wet cycling has no significant impact on the failure mode of dolomite, which remains shear failure or mixed shear-tensile failure. Dry-wet cycling leads to the dissolution of internal soluble salts and colloids in dolomite, as well as the initiation and propagation of cracks, while cyclic loading and unloading at different upper limits accelerate crack propagation and the destruction of cementing materials between particles. When these two factors act together, the deterioration rate of the rock's physical properties is faster than under either factor alone.