Characteristics and mechanism of landslide-debris flow chain disaster in low mountain and hilly terrain
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摘要:
2019年6月10—13日，龙川县发生持续强降雨，导致全县境内发生大量滑坡、泥石流灾害，贝岭镇米贝村是三个重灾区之一。本文以贝岭镇米贝村6号沟发生的滑坡-泥石流链生灾害为研究对象，在野外精细化调查测量基础上，结合数值模拟分析与计算，对链生灾害特征与成灾机理展开研究。研究发现：①6号沟内共发育7处浅层土质小型滑坡，仅3号滑坡体与部分6号滑坡体转化为泥石流，构成泥石流主要物源，其余滑坡未构成持续性影响；②持续降雨下渗，坡体由非饱和向饱和状态转变，坡表形成连续饱和区，孔隙水压力的增加与孔隙水的软化促使土体强度降低，加之坡体饱和自重的增大，斜坡发生浅表层失稳破坏；③降雨的持续下渗与支沟沟源“漏斗状”地形下的地表汇水快速增大滑坡松散堆积体内的含水率，促使其物理性质发生变化，在重力势能下呈流态状启动、运动转化为泥石流。降雨结构影响滑坡-泥石流链生过程，前期降雨引发滑坡、后期降雨启动形成泥石流，滑坡与泥石流的发生表现出阶段性特征。研究成果有助于指导当地政府进一步开展滑坡-泥石流链生灾害的防灾减灾工作，也为该地区未来区域预警研究工作提供理论支撑。
Abstract:From June 10 to 13, 2019, continuous heavy rainfall occurred in Longchuan County, resulting in a large number of landslides and debris flows in the county. Mibei village is one of the three hardest hit areas. Taking the landslide debris flow chain disaster in Mibei village No.6 gully of Beiling town as the research object, this paper studies the characteristics and disaster mechanism of chain disaster on the basis of field fine investigation and measurement, combined with numerical simulation analysis and calculation. It is found that: ①there are 7 soil landslides in the No.6 gully. Only NO.3 landslide mass and part of NO.6 landslide mass are transformed into debris flow, which constitutes the main material source of debris flow, and the other landslides do not constitute a sustainable impact; ②With continuous rainfall infiltration, the slope body changes from unsaturated to saturated state, and a continuous saturated zone is formed on the slope surface. The increase of pore water pressure and the softening of pore water reduce the strength of soil. In addition, the increase of saturated weight of slope body leads to the instability and failure of shallow surface layer of slope; ③The continuous infiltration of rainfall and the surface catchment under the "funnel" terrain of the branch gully source rapidly increase the water content in the loose accumulation of the landslide, promote the change of its physical properties, start and move in a flow state under the gravitational potential energy, and transform it into debris flow. The rainfall structure affects the chain process of landslide debris flow. The landslide is caused by early rainfall and the debris flow is formed by later rainfall. The occurrence of landslide and debris flow shows phased characteristics. The research results are helpful to guide the local government to further carry out the disaster prevention and reduction of landslide debris flow chain disasters, and also provide theoretical support for the future regional early warning research in this area.
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Key words:
- heavy rainfall /
- granite residual soil /
- chain disaster /
- disaster mechanism
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