Energy evolution and constitutive model for damage of degraded limestone under coupling effects of hydrodynamic-stress-chemical corrosion

The reservoir water level undergoes annual cyclical fluctuations, which leads to the state of hydrodynamic erosion of wetting-drying cycles of the bedrock in the hydro-fluctuation belt. In addition, the self-weight of the overlying rock mass also reduces the strength of the bedrock. To study the deterioration law of the rock mass under the coupling of hydrodynamic- stress-chemical corrosion, the degradation tests are conducted on limestone samples based on the field investigations. The law of energy evolution of limestone under the coupling of hydrodynamic-stress-chemical corrosion is elucidated, and the constitutive model for damage is proposed. The results show that according to the energy rate-strain curve, the rock failure process can be divided into five stages: compaction of vulnerable zone, microfracture closure, elastic deformation, microfracture extension, and post-peak failure. With the increase of the degradation stress, part of the dissipative energy is released in advance, and the strain at which the dissipated energy equals the elastic energy gradually decreases. The sensitivity of the total energy to the degradation stress increases with the increase of the wetting-drying cycles. The coupling mechanism of hydrodynamic-stress-chemical corrosion is revealed. The constitutive model for damage considering the deterioration of limestone at the compaction stage under the coupling of hydrodynamic-stress-chemical corrosion is proposed, which has higher prediction accuracy and can provide some theoretical guidance for disaster prediction and prevention in reservoir areas.