寒区危岩主控裂隙扩展演化机制研究

The Evolutionary Mechanism of Control Fracture Propagation of Dangerous Rock in Cold Region

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。

Instability of dangerous rock frequently depends on control fracture propagation,to distinctly understand change of stability to the dangerous rock;this article mainly studies the evolutionary mechanism of control fracture propagation of dangerous rocks in the cold region.Considering interaction of frost-heave load and gravity load,norm of cracking to the composite fracture was established on the basis of energy density factor,a length relation of fracture propagation under frost-heave stress and gravity stress was derived by means of Griffith criterion.Taking a toppling dangerous rock in the Xinjiang Tianshan area as an Example,it discussed the evolutionary laws of control fracture propagation.The results showed that the evolutionary of control fracture propagation is the development from stable extension to unstable extension.In the four stages of calculation,fracture propagation is in stable state for first three phases,in stable propagation of fracture,length of fracture propagation reaches each time about 2mm,and its increasing speed keeps relative constant.Fracture propagation of the last stage is in unstable condition,its length is each time more than 4mm,and rises in index,at the same time,and the risk of instability of dangerous rock is increasing.This paper provides theoretical basis for estimation of stability,trend prediction of its development and prevention of dangerous rock.