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危岩的失稳往往主控于主控裂隙扩展。为清楚了解危岩稳定性变化情况,主要针对寒区危岩主控裂隙扩展演化机制进行研究。基于能量密度因子理论,建立危岩受冻胀荷载和自重荷载共同作用下的复合型裂隙开裂判据,运用Griffith准则,推导了在单次冻胀应力和危岩自重应力下裂隙扩展长度关系式,以新疆天山倾倒式危岩为例,探讨了该危岩主控裂隙扩展演化规律。结果表明,危岩主控裂隙扩展演化是从平稳增长向指数增长演化扩展。在计算的4个阶段中,前3个阶段裂隙平稳扩展,裂隙扩展长度增速相对恒定且扩展长度均值约每次2.0mm,最后一个阶段裂隙扩展呈指数趋势增长且扩展长度超过每次4.0mm,危岩失稳的风险极速增大。以此为深入研究寒区危岩稳定性评价、裂隙扩展趋势预测以及危岩防治提供一定的理论依据。
Dangerous rock instability is often dominated by the expansion of the master crack. In order to understand the change of the stability of the dangerous rock, the research mainly focuses on the evolution mechanism of the main crack growth of the dangerous rock in the cold area. Based on the theory of energy density factor, the criterion of composite fracture cracking under the joint action of frost heave and self-weight load was established. Based on the Griffith criterion, the relationship between the crack propagation length under single-frost heave stress Taking the Tianshan dumping dangerous rock in Xinjiang as an example, the evolution rules of the main crack propagation in the dangerous rock are discussed. The results show that the evolution of the host rock fissures evolves from a steady growth to an exponential growth evolution. In the first four stages of calculation, the fractures propagate smoothly, the growth rate of crack propagation length is relatively constant and the average length of expansion is about 2.0mm each time. In the last stage, the fracture propagation increases exponentially and the expansion length exceeds 4.0mm , The risk of unstable rock instability increased rapidly. This provides a theoretical basis for further study on the stability evaluation of dangerous rock in the cold area, the prediction of the crack propagation trend and the prevention and treatment of dangerous rock.