台风暴雨型泥石流启动机理物理模型试验研究

Physical model test on initiation mechanism of typhoon rainstorm-triggered debris flow

台风暴雨型泥石流具有很高的突发性、群发性和破坏性,对这种特殊类型泥石流启动机理的研究尤为重要。以“利奇马”台风引发的安徽宁国抽水蓄能电站库区泥石流灾害为典型案例,在现场勘探、调查、测试的基础上,查明了泥石流沟谷特征、形成条件及物源分布;采用人工降雨物理模型试验方法,监测降雨过程中土体孔隙水压力、体积含水率、土压力和侵蚀特征等指标变化,研究了台风暴雨型泥石流的启动机理。结果表明:①台风暴雨型泥石流过程分为降雨入渗、超渗径流、物源侵蚀堆积、短历时强降雨启动4个阶段。②台风暴雨型泥石流发生在浅层土体达到高含水率和高孔隙水压力之后,需要前期一定的累积降雨。③较小雨强条件下沟谷产生稀性泥石流,降雨强度的陡增引起径流强度及侵蚀作用急剧加强,大量固体物质启动,暴发的泥石流由稀性转为黏性,沟口可见较大规模堆积扇。④整个沟谷均可见侵蚀沟道不同程度贯通分布,沟道侵蚀深度随高程的降低呈现增大趋势。研究结果可为台风暴雨型泥石流灾害风险防控提供参考。

Typhoon rainstorm-triggered debris flows exhibit high suddenness,mass occurrence,and destructiveness.Therefore,researching the initiation mechanisms of this specific type of debris flow is particularly crucial.Taking the debris flow disaster in the reservoir area of Anhui Ningguo Pumped Storage Power Station triggered by Typhoon“Lekima”as a typical case,the characteristics,formation conditions,and sediment distribution of debris flow gullies were identified based on field explorations,investigations,and tests.Utilizing the physical model test of artificial rainfall,the changes in indicators such as pore water pressure,volumetric water content,soil pressure,and erosion characteristics were monitored during the rainfall,thus the initiation mechanism of typhoon rainstorm-triggered debris flow was studied.The results showed that:①The outbreak of the typhoon rainstorm-triggered debris flow can be divided into four stages,namely rainfall infiltration,super-saturation runoff,erosion and accumulation of sediment sources,and initiation under short-duration intense rainfall.②The typhoon rainstorm-triggered debris flow occurs after shallow soil reaches high water content and high pore water pressure,which requires a certain amount of accumulated rainfall beforehand.③Under conditions of lower rainfall intensity,watery debris flows may occur in the gully;however,a sudden increase in rainfall intensity intensifies runoff and erosion significantly,initiating a large amount of solid material.The debris flow transits from watery to viscous,with visible large-scale accumulation fans accumulating at the gully mouth.④Penetration of varying degrees among eroded channels was observed throughout the gully,and the erosion depths increased with the decreasing elevation.These findings can provide insights into the prevention and control of typhoon rainstorm-triggered debris flow disasters.