The instability of dangerous rock masses is primarily caused by the stress intensity factor at the primary structural plane exceeding the fracture toughness of the rock bridge section, which results in the propagation of fractures. Additionally, in cold regions, the fracture toughness of these rock masses gradually decreases due to freeze–thaw cycles. Initially, considering the deterioration of type I and type II fracture toughness in the rock bridge section and the frost heaving force between structural planes, an assessment model for the stability of dangerous rock mass under freeze–thaw cycles is established. Secondly, utilizing the theory of circular hole expansion, along with the Mohr-Coulomb yield criterion and maximum tensile stress criterion, a model is constructed to simulate the degradation of type I and type II fracture toughness in rock bridge segments under the influence of freeze–thaw cycles. The validity of this model was subsequently verified through experimental validation. Finally, through engineering case studies, the degradation pattern of the stability of dangerous rock formations under the action of freeze–thaw cycles was analyzed. The study reveals that the decreasing stability of dangerous rock mass under freeze–thaw conditions is intricately linked to the internal friction angle, elastic modulus, and initial tensile strength of the rocks. Notably, the long-term stability of hard and coarsely textured dangerous rock mass under such conditions generally improves. Conversely, the tensile strength of the rock bridge segment elevates, which is beneficial for the long-term stability of the rock mass. When the residual debris ratio exceeds 0.25, the instability of the rock mass deteriorates more modestly. To maintain long-term stability, managing debris loss or injecting fillers into the pores can be effective strategies.

中文翻译：

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冻融循环下危岩体断裂韧性劣化及失稳模型分析

危岩失稳主要是由于原生结构面应力强度因子超过岩桥断面的断裂韧度，导致裂缝扩展所致。此外，在寒冷地区，由于冻融循环，这些岩体的断裂韧性逐渐降低。首先，考虑岩桥断面Ⅰ、Ⅱ类断裂韧性的恶化以及结构面间的冻胀力，建立了冻融循环下危岩体稳定性评价模型。其次，利用圆孔膨胀理论，结合Mohr-Coulomb屈服准则和最大拉应力准则，建立模型模拟冰冻作用下岩桥节段I型和II型断裂韧性的退化。解冻周期。随后通过实验验证验证了该模型的有效性。最后，通过工程实例研究，分析了冻融循环作用下危险岩层稳定性的退化规律。研究表明，冻融条件下危险岩体的稳定性下降与岩石的内摩擦角、弹性模量和初始抗拉强度密切相关。值得注意的是，在这种条件下，坚硬、结构粗的危险岩体的长期稳定性普遍提高。反之，岩桥段的抗拉强度升高，有利于岩体的长期稳定。当残屑比超过0.25时，岩体的失稳性恶化程度较轻。为了保持长期稳定性，控制碎屑损失或向孔隙中注入填料可能是有效的策略。