含构造节理的崩塌体动力破碎特征

Dynamic fragmentation characteristics of rock avalanche with tectonic joints

近年来西南地区崩塌灾害频发,严重影响区域生态环境和人类活动。为明确崩塌体运动过程中的破碎特征,基于对贵州毕节纳雍县鬃岭崩塌的野外地质勘察,使用离散元颗粒流方法模拟了鬃岭崩塌在破坏及堆积阶段的动力破碎过程,并对崩塌体中破碎体的最大弗雷特直径(feret’s diameter)分布特征进行统计分析。结果表明:(1)重力作用下鬃岭崩塌内部构造节理迅速贯通,将崩塌体分割为大量破碎块体,最终沿顺倾节理面滑下。(2)在崩塌前期破坏及后续堆积过程中均存在明显的破碎现象,具体表现为初始破坏时的大范围解体与后续堆积过程中的摩擦拉裂破碎。(3)采用双参数Weibull分布模型及分形几何理论拟合了不同时刻破碎体粒径分布曲线,结果显示崩塌体在堆积阶段(t=21.7~72.4 s)的破碎程度弱于前期破坏阶段(t=0~21.7 s)的破碎程度,破碎体的分形维数及细粒径破碎体的占比在整个运动过程中不断增大,再次论证了崩塌体破坏及堆积全过程中的破碎解体现象。研究结果为揭示鬃岭崩塌的动力破碎机理提供了理论依据,为西南山区崩塌灾害的防治提供了科学指导。

In recent years,rock avalanche disasters have been occurring frequently in southwest China,which seriously affect the regional ecological environment and human activities.To understand the fragmentation characteristics of the avalanche masses during their movement,this study is based on the field investigation of the rock avalanche in Zongling Town,Nayong County.The dynamic fragmentation process of the rock avalanche during the failure and accumulation stages was simulated using the particle discrete element method.Additionally,the distribution characteristics of the maximum feret’s diameter of the fragments within the rock avalanche mass were statistically analyzed.The results show that:(1)Under the effect of gravity,the internal structural joints of the rock avalanche rapidly interconnected,dividing the avalanche mass into numerous fragmented blocks that eventually slid along the down-dip joint surfaces.(2)The collapse exhibited significant fragmentation phenomena in the entire movement process,with extensive disintegration during the initial failure and friction-induced tearing and cracking fragmentation during the accumulation stage.(3)The feret’s diameter distribution curves of the fragments at different time intervals were fitted using Weibull two-parameter distribution model and fractal geometry theory.The results showed that the fragmentation degree of the avalanche during the accumulation stage(t=21.7 to 72.4 s)was weaker than that during the initial failure stage(t=0 to 21.7 s).The fractal dimension of the fragments and the proportion of fine-grained fragments continuously increased throughout the entire movement process,once again confirming the fragmentation and disintegration phenomena during the entire process of failure and accumulation.The research findings provide a theoretical basis for revealing the dynamic fragmentation mechanism of the Zongling rock avalanche,and provide scientific guidance for the prevention and control of rock avalanche disasters in the mountainous areas of southwest China.