西藏樟木后山危岩崩塌颗粒离散元数值分析

Numerical analysis of Tibet Zhangmu dangerous rock collapse by discrete element method

崩塌危岩是高陡岩质边坡浅表层破坏常见的动力地质灾害方式之一,它突发性强,随机性大,速度快,发生猛烈,一直是边坡工程勘察中的重点。对西藏樟木后山高陡边坡危岩进行了现场勘察,分析研究了危岩崩塌体的分布范围。利用PFC3D模拟了在降雨件下危岩崩塌危岩的运动轨迹、速度及不同摩擦系数崩塌体的堆积特征。计算分析结果表明,崩塌危岩运动路径受地形地貌影响较大,与地面发生碰撞,多次改变行进方向,简化二维计算可能得出错误结论;坡面摩擦系数影响崩塌危岩的堆积形态,摩擦系数越小,堆积体位置越远,运动状态易表现流态性状。坡面摩擦系数取1.2时,模拟结果与实际较为吻合;崩塌危岩主要危害的范围为陡崖下部武警二营至樟木沟口一带。利用PFC3D模拟危岩崩塌运动可以初步确定崩塌体三维堆积形态及影响范围,为防灾减灾工程设计提供有益参考。

Collapse of dangerous rocks is one of the most common geological dynamics hazards of high and steep shallow rock slope. It is sudden and strong, random, high speed and violent; so it is the focus of slope engineering survey. On the base of on-site investigation of dangerous rocks of Tibet Zhangmu Mountain, the distribution range of dangerous rock bodies is analyzed. The trajectory of collapse dangerous rocks, speed and characteristics of the body collapse accumulation of the different coefficients of friction is simulated by PFC3D in the condition of rainfall. The results show that the trajectory of collapse dangerous rocks is influenced by topography of slope, multiple impacts with the ground and repeated changes of direction, simplifying dimensional calculations may draw the wrong conclusions. Slope surface coefficient of friction affect the accumulation of forms of collapse of dangerous rocks, the smaller friction coefficient, the farther accumulation body position, and the easier performing flow state. Slope coefficients of friction 1.2, the simulation results are more consistent with the actual; The area of collapse dangerous rocks is the lower cliffs from Armed two camps to Zhangmu trench opening. PFC3D simulation of dangerous rocks collapse body movement can initially determine three-dimensional accumulation form and the influence scope, and provide a useful reference for disaster prevention and mitigation engineering design.