The mode-I fracture toughness of rock is one of the key mechanical indexes to measure the resistance of rock to its own crack propagation. The mode-I fracture toughness of rock mass in cold region is normally deteriorated by freeze–thaw cycle under temperature variation. Based on the theory of pore expansion, the meso-deterioration mechanism of pores in rock under the action of ice frost heave is analyzed, and the meso-deterioration model of tensile strength is formulated. The evolution equation of mode-I toughness is built according to the relationship between the mode-I fracture toughness and the tensile strength. The predicting model is validated by comparing with actual test. The results show that the falling of freezing temperature imposed a significant effect on the mode-I fracture toughness when the freezing temperature is above −10 °C. The migration of pore water decreases when the freezing time is between 2 h and 8 h, which leads to the sensitivity of fracture toughness to freezing time. The deterioration range of mode-I fracture toughness decreases gradually when the debris loss ratio is lower than 0.9. The control of debris loss is essential for the long-term stability of rock mass engineering in cold regions.

岩石的I型断裂韧度是衡量岩石对自身裂纹扩展阻力的关键力学指标之一。寒冷地区岩体的I型断裂韧性通常在温度变化下因冻融循环而恶化。基于毛孔扩张的理论，内消旋冰冻胀的作用下在岩石孔隙-deterioration机理进行了分析，并且内消旋- 建立抗拉强度劣化模型。根据I型断裂韧度与抗拉强度的关系，建立I型韧度演化方程。通过与实际测试的比较，验证了预测模型。结果表明，当冷冻温度高于-10℃时，冷冻温度的下降对I型断裂韧性产生显着影响。冻结时间在 2~8 h 时孔隙水的迁移减少，导致断裂韧性对冻结时间的敏感性。当碎屑损失率低于0.9时，I型断裂韧性的劣化范围逐渐减小。控制碎屑流失对于寒冷地区岩体工程的长期稳定性至关重要。