两类泥石流形成机制的再讨论

Re-discussion on the formation mechanism of two types of debris flows

泥石流是大坡度山区常见的自然灾害,从其触发动力因子溯源常划分为水力类和土力类两大基本类型。水力类泥石流起动的核心控制因素为水流对物源的冲击和拖曳力,与水流(或水沙浆体)强度密切相关;土力类泥石流起动的核心过程为滑坡(库伦破坏)和土体液化,主要受控于孔隙水压力(和土体含水量)。两类泥石流过程赖以发育的地质、地貌和环境条件显著不同,形成机制和关键因子迥异,但两类过程仍可以(且有必要)统一在一个宏观多相流物质输移体系中进行分析探讨,这对于进一步明晰泥石流易发环境(地质、地貌、气候)、关键要素和起动条件,有针对性地构建监测预警体系,并提出有效防控治理策略有重要的科学价值和实践意义。

Debris flows are common natural hazards in high gradient mountain areas. Two basic types of debris flows are often classified when tracing back their triggering dynamics:hydraulically related or geo-mechanically related. The core control factors for the initiation of hydraulically related debris flow are the impact and drag force of the water flow on the sediment deposits,which are closely related to the flow(or slurry)intensity;and the core process of the initiation of geo-mechanically related debris flow is landslide(Coulomb failure)and soil liquefaction,which is mainly controlled by pore water pressure(and soil water content). The two types of debris flow processes rely significantly on quite variant geological,geomorphological and environmental conditions,hence their formation mechanisms and key factors are very different. However,on the macroscopic perspective,the two types of processes can be still(and necessary)unified as multiphase flow material transport system for theoretic analysis and discussion. This is of great scientific value for further clarification of the environment(lithology,landform,and climate)orientation,key elements and initiation conditions of debris flows. It also has practical significance for constructing suitable monitoring and early warning system in a targeted manner,and correspondingly proposing effective prevention and control strategies for debris flows.