Effect of acid corrosion on shear creep behavior of Permian carbonaceous shale in Southwest China

To quantify the acid corrosion characteristics and shear creep behavior of carbonaceous shale under acid corrosion, immersion tests and acid corrosion shear creep tests were conducted at different pH values. The shear fracture surface characteristics of the damaged samples were observed using scanning electron microscopy (SEM). The mechanisms of acid corrosion and its shear creep effects on carbonaceous shale were elucidated. The results indicate that the higher the initial concentration of H + , the greater the wave velocity degradation rate and mass damage rate of the sample after acid etching reaction. The mass damage rate, wave velocity degradation rate of carbonaceous shale, and the pH of the solution first increased linearly and rapidly with time, followed by a nonlinear decrease, and finally reached a stable state. When the number of dry-wet cycles is constant, the higher the H + concentration, the greater the creep deformation, the longer the decelerating creep time, the higher the steady-state creep rate, and the lower the long-term strength. Acid corrosion induces mineral dissolution, increasing pore density. The products of acid corrosion reactions and clay minerals migrate and precipitate along paths influenced by dry-wet cycles, resulting in overall structural damage and decreased mechanical strength in carbonaceous shale.