冻融循环作用下危岩体滑移破坏数值优化分析

Numerical Optimization Analyses of Dangerous Rock Mass Sliding Failure Under Freeze-thaw Cycles

冻融循环作用是寒区危岩体崩塌失稳的主要诱因,对寒区危岩体滑移破坏的孕灾因素进行数值优化分析尤为重要。首先,基于极限平衡理论,考虑危岩体贯通段结构面冻胀力、未贯通段岩石黏聚力劣化及冻结深度演化,建立冻融循环作用下滑移式危岩体稳定性分析模型;其次,基于岩石冻胀理论,考虑冻结过程中水分迁移推导得到贯通段冻胀力计算方法;再次,将岩石细观孔隙抽象为无数圆形孔洞,根据圆孔扩张理论和莫尔–库伦屈服准则分析孔隙冻胀破坏过程,构建冻融循环作用下未贯通段岩石黏聚力细观劣化模型;最后,通过改进Stephan经验公式得到未贯通段岩石冻结深度随冻融循环次数演化的计算方法。结合工程算例分析各敏感参数对危岩体稳定性的影响发现:滑移式危岩体稳定性随冻融循环次数的增加呈先快后缓的下降趋势;危岩体稳定性系数与冻结温度呈正相关,相同冻结温度下,危岩体稳定性系数的下降随冻融循环次数增加出现明显的边际递减效应;危岩体稳定性系数与岩屑流失比呈负相关,且岩屑流失比会同时改变稳定性劣化趋势和劣化程度,控制岩屑流失比有利于寒区危岩体的长期稳定性。

The action of freeze-thaw(F–T) cycles is the main inducement for the collapse and instability of dangerous rock mass in cold regions,and it is particularly important to carry out numerical optimization analysis on the disaster pregnant factors of sliding failure of dangerous rock mass in cold regions. Firstly, based on the limit equilibrium theory, the stability analysis model of sliding dangerous rock mass under the action of F–T cycles was established by considering the frost heave force of through section structural plane, the deterioration of the cohesive force of the locked section, and the evolution of the freezing depth. Secondly, based on the theory of rock frost heave and considering the water migration during the freezing process, the calculation method of the frost heave force of the through structural plane section was derived. Thirdly, the mesoscopic defects of rock were simplified to numerous circular pores. According to the expansion theory of circular pores and the Mohr–Coulomb yield criterion, the process of pore frost heave failure was analyzed, and the meso degradation model of rock cohesion in the non-penetrated section under the action of the freeze-thaw cycle was constructed. Finally, the calculation method of the evolution of the rock freezing depth of the locked section with the number of F–T cycles was obtained by improving Stephan’s empirical formula. Combined with the engineering calculation example to analyze the influence of each sensitive parameter on the stability of the dangerous rock body, it was found that the stability of sliding dangerous rock mass showed a fast and then slowly declined with the increase of the number of F–T cycles. The stability coefficient of sliding dangerous rock mass was positively correlated with the freezing temperature. At the same freezing temperature, the stability coefficient decreased with the increase of the number of F–T cycles with a significant marginal decreasing effect. The stability of dangerous rock mass was negatively correlated with the rock debris loss ratio, and the rock debris loss ratio changed both the trend of stability deterioration and the degree of deterioration. Controlling the rock debris loss ratio was conducive to the long-term stability of the dangerous rock mass in cold regions.