Deformation characteristics and fracture damage model of freezing weakly cemented jointed rock masses

In the frozen state, rock masses characterized by weak cementation and nodular joints exhibit the effects of ice infill, frost-heave reinforcement, and frost-heave-induced damage. Consequently, the deformation modulus and fracture toughness of these rock masses are influenced by the frozen temperature, ultimately modifying the propagation process of fractures within structural planes. Considering the unfrozen rock mass as a composite consisting of soft material arising from compressible pores and hard material constituted by the rock skeleton, the entire deformation process of the frozen rock mass is categorized into a compaction stage and a post-compaction stage. Constitutive relationship equations are formulated separately for the compaction component and the skeletal component. Taking into account the reinforcing effect of low-temperature environments on the mechanical properties of rock mass, as well as the frost-heave damage effect, methods for calculating frozen negative damage, frost-heave damage, and wing crack damage variables have been developed. Based on these methodologies, a macro–micro damage model for the skeletal part of the rock mass has been established. The rationality of this model has been verified through loading tests on frozen jointed rock mass. Furthermore, the model has been employed to explore the influence rules of frozen temperature, rock mass properties, and joint inclination angles on the mechanical properties of rock mass. The research findings indicate that the freezing temperature significantly affects both the compaction and elastic phases of the rock mass, and the compressive strength increases correspondingly as the freezing temperature decreases. The total mesoscopic damage due to loading diminishes with decreasing frozen temperature, indicating that the rock mass becomes more brittle at lower temperatures. A higher initial tensile strength is associated with greater overall rock mass strength, accompanied by lesser wing crack damage and frost heave damage. The influence of joint inclination on the mechanical properties of frozen rock is more pronounced.