颗粒反序现象及对滑坡碎屑流冲击作用的影响

滑坡碎屑流的堆积形态、运动速度及冲击力影响着滑坡碎屑流的致灾程度。颗粒反序现象是滑坡碎屑流动力行为的典型特征,探究反序现象的成因机制、反序堆积过程中冲击力变化的主控因素是滑坡碎屑流防灾减灾工作的重要切入点。运用三维离散元素法,结合模型试验的结果,以控制粒径d_(60)为参数,探索了滑体颗粒运动过程中的反序分离对滑体的堆积形态、运动速度及冲击力的影响,并对滑坡碎屑流颗粒反序现象的成因机制进行了讨论。研究表明,滑坡碎屑流运动过程中的颗粒分选能大大增强滑体的流动性、平均速度峰值及最大冲击力,滑体最终形成反序堆积结构。对于单一粒径滑体模型,粒径为14 mm时滑体流动性最差,滑体平均速度峰值和冲击力峰值随着粒径的增大而增大;对于混合粒径滑体模型,滑体流动性、平均速度峰值和冲击力峰值随控制粒径d_(60)尺寸的增大而增大;颗粒反序现象的形成是由消散压力、振动筛分、大颗粒碰撞分离、小颗粒率先停积等因素共同作用的结果。

A study on inverse grading and its influence on impact effect of landslide-debris flow

The dynamic characteristics of landslide-debris flow, such as the accumulation pattern, velocity and impact force, affect the hazard degree of landslide-debris flows. Inverse grading of particles is a typical characteristic of the dynamical behavior of landslide-debris flow. Exploring the mechanism of the inverse grading and the main controlling factors of landslide impact is important. Combining with the result of model tests, and taking the controlling particle of d60 as a factor, the three-dimensional Discrete Element Method was used to study the influence of inverse grading on the dynamic characteristics of landslide-debris flow, such as velocity, accumulation and impact force. The genetic mechanism of inverse grading was studied. The results show that the particle segregation and inverse grading in rock fragment flowing could greatly enhance the mobility, average velocity and impact force of landslide-debris flow. For the simulated landslide-debris flow with the single particle size, the mobility of landslide of particle size of 14 mm was the lowest. Besides, the maximum average velocity and maximum impact force increased with the particle size. For the simulated landslide-debris flow with different particle sizes, the mobility, the mean peak velocity and impact force all increased with the controlling particle size. The cause of inverse grading was a coupling effect of the gravity dispersion, the kinematic sieving, large particles segregation and the earlier accumulation of small particles.