Frozen effect of microcrack growth on compressive fracture in saturated brittle rocks

The frozen effect on compressive fracture behavior in saturated brittle rocks, induced by microcrack propagation, is crucial for assessing the safety and stability of underground engineering projects in cold regions. However, the micro–macro fracture mechanism remains unclear during compressive failure in frozen saturated brittle rocks. This paper aims to develop a micro–macro fracture model with the frozen effect in saturated brittle rocks. This model is formulated by combining the low temperature-dependent fracture toughness K_IC, friction coefficient μ, skeleton contractile stress P_t, frost heave stress P_f, and cohesive stress P_c between crack surfaces into the previous wing microcrack growth model. An improved stress intensity factor at wing crack tips, incorporating the frozen effect, is proposed. This study investigates the frozen effects on saturated rock’s stress–strain curve and compressive strength by combining the proposed stress intensity factor, rock fracture criterion, and crack-strain damage relation. The frozen effect reduces the pore compaction phase, as evidenced by the gradual disappearance of the concave trend in the pre-peak stress–strain curve. Additionally, compressive strength increases compared to room temperature during progressive compressive failure. The validity of the presented model results is verified through published experiments. The effects of confining pressure and microcrack characteristics on the compressive strength of rocks are discussed at different temperatures. Under compression, the frozen strengthening mechanisms of saturated brittle rocks offer valuable insights for the design and safety evaluation of cold-region engineering projects.