Water Resources and Power

To investigate the performance evolution of expansive soft rock in a northwest China under acidic wet-dry cycles, compression tests were conducted at varying acidity levels and wet-dry cycle counts. The physical and mechanical properties and the changes of mineral composition were systematically analyzed by combining with ultrasonic testing, electron microscopy, and chemical analysis. The damage evolution mechanism of expanded rock under the action of cyclic hydraulic failure and acid erosion was revealed. The results show that acidic fluids significantly increase water-rock interaction, intensifying the effects of wet-dry cycles. Mechanical parameters decayed logarithmically with increased acidity and cycles. Rapid mineral dissolution under hydraulic erosion weakened intergranular contact, leading to microfracture development and greater ultrasonic energy dissipation, ultimately degrading the rock's mechanical properties. The increase of solution acidity increased the degree of process deterioration and intensified the long-term strength attenuation of rock mass under the action of early dry-wet cycles.