滑坡型泥石流的转化机理研究

Transformation Mechanism of Landslide Debris Flow

滑坡一旦转化为泥石流,其运动距离将显著增加,会严重威胁人民的生命和财产安全,而揭示滑坡型泥石流的转化机理是对其进行预测预报与防治的前提。以新疆乌恰县托云乡乔库而滑坡型泥石流为研究对象,利用遥感影像、现场调查和室内实验(包括颗分、直剪和环剪试验),对其转化机理进行研究。结果表明:受有限降水条件的影响,乔库而滑坡型泥石流物源区的松散堆积物失稳后不能直接形成泥石流,而是首先形成滑坡,滑坡体在长距离运移过程中,一方面由于土体颗粒破碎和铲刮作用,导致滑坡土体运移过程中细颗粒物质逐渐增加,土体抗剪强度不断降低;另一方面则是在土体颗粒破碎作用下,土体发生剪缩,导致土体孔隙水压力不断增大,产生超孔隙水压力,土体抗剪强度急剧下降甚至发生液化,最终转化为泥石流。另外,通过环剪试验结果可知,对于乔库而泥石流,滑坡体转化为泥石流的土体临界初始含水率在20%~27%之间,而其低于20%,则滑坡体无法转化为泥石流。

Once landslides are transformed into debris flow,their movement distance will increase significantly,which seriously threatens the safety of people's lives and property.Therefore,revealing the transformation mechanism of landslide debris flow is the premise of its prediction and prevention.Taking Qiaokuer landslide debris flow in Tuoyun,Wuqia County,Xinjiang as the study object,this paper studies the migration mechanism by using remote sensing images,field investigation and laboratory experiments(including grain separation,direct shear and ring shear tests).Results show that because of limited precipitation conditions,landslide debris flow source area can not directly form debris flow after the debris instability,but first form landslide.In the process of long distance transport,fine particulate matter in the process of migration of soil increase gradually due to the influence of soil particles broken and chipped role,which decreased soil shear strength.The soil shear shrinkage occurs under the effect of particle breakage,which increases the pore water pressure,and the shear strength of soil falls sharply due to the presence of excess pore water pressure,eventually liquefies soil landslide into debris flow.In addition,the critical initial moisture content of the sliding body transforming into the debris flow is between 20%and 27%,below which the sliding body cannot be converted into the debris flow.