The macro-meso damage model for jointed rock mass under the sequential effects of freeze-thaw cycles and compressive shear load

In cold regions, the macro-meso damage in jointed rock masses accumulates continuously due to sequential freeze-thaw cycles and compression shear load, resulting in a gradual decrease in the fracture toughness of the rock masses. Fracture instability arises in the rock mass once the stress intensity factor at the joint tip exceeds the fracture toughness of the rock. Recognizing the macro- and mesoscopic damage in rock masses as indicators of the compromised integrity of the intact rock area, a composite damage model for jointed rock masses is developed by integrating initial macro- and mesoscopic damage, freeze-thaw damage, and load-induced damage. Utilizing this model, the rock meso-pores are abstracted into countless elliptical fissures, and the freeze-thaw damage process of rock meso-pores is analyzed, resulting in computational methods for the rock meso-damage variables under the action of freeze-thaw cycles. By integrating fracture mechanics with strain energy theory, a computational method for macroscopic damage variables caused by initial joints and propagating wing cracks has been derived. Upon comparing the theoretical computational results with the experimental findings, it is observed that there is a good agreement between the two, thereby validating the model's rationality.