碎屑流冲击挡墙的土拱效应研究

Study on soil arch effect of dry debris flow for impact barricade wall

为揭示干碎屑流冲击挡墙过程中碎屑颗粒在底板、底板与挡墙之间的土拱效应,探讨了土拱效应的形成机理、冲击力拱的形成特征以及对冲击力分布变化的影响,为碎屑流的工程防护提供理论支持。利用PFC模拟方法和模型试验的数据资料,进行了不同底板坡度下干碎屑流冲击挡墙的数值模拟分析。发现碎屑流运动中摩擦作用和碰撞机制导致的底板的颗粒之间、垂直底板方向上不同高度颗粒之间的速度差异是土拱效应的形成机理;碎屑流颗粒之间以及颗粒与底板间的摩擦作用引起的冲击力迹线的偏转较小,形成小冲击力拱;颗粒的冲击力迹线在碎屑流受挡墙的阻止时产生较大的偏转叠加,在底板与挡墙间形成大冲击拱。研究结果表明:碎屑流的运动机理产生土拱效应,土拱效应的特征不仅影响了碎屑流冲击力的分布变化,还导致了冲击力随挡墙高度的非线性分布。

This paper aims to reveal the soil arch effects of dry debris flow on the bottom and between the back board and wall, explore the formation mechanism of soil arch effects, formation characteristics of impact force arch and its influence on distribution change of impact force, so as to provide the theoretical guide for engineering pro- tection of debris flow. Therefore, based on PFC numerical simulation program and data of model experiments, nu- merical simulations of the impact of dry debris flow on a barricade wall were conducted for different slopes. It is found that, the formation mechanism of soil arch effect is the velocity differences among the grains and grains of dif- ferent heights in the perpendicular bottom direction because of friction and collision of dry debris flow in the move- ment. The impact traces deflected by friction among grains and between grain and floor is small, which results in the formation of small impact arch. When the dry debris flow is blocked by the wall, the impact force traces deflec- ting is large, which results in the formation of large impact force arches between the floor and barricade wall. The results indicate that, it is the motion mechanism of dry debris flow that induces the soil arch effect, and the soil arch effect not only influences the distribution and change of the impact force of dry debris flow, but also brings a- bout the non - linear distribution of impact forces at different height of the barricade wall.