坡面泥石流形态和堆积特征研究

Morphological and depositional characteristics of slope debris flow

坡面泥石流是发育在陡峭沟、坡中的不稳定岩土体失稳后转化形成,具有分布广、数量多等特点。为了有效区分滑坡型和冲蚀型坡面泥石流,对研究区进行了野外调查和无人机拍摄,首先分析了两种类型泥石流的形态特征和颗粒组成差异;再将地形陡峭指数和堆积区坡度、流动路径长度、流动比结合起来进一步分析两种坡面泥石流流动特征,并对地形陡峭指数进行了修正。结果表明:冲蚀型坡面泥石流堆积物以粗颗粒为主,滑坡型泥石流堆积物以细颗粒为主;冲蚀型坡面泥石流堆积扇坡度要高于滑坡型泥石流,但是流动性要稍弱于滑坡型泥石流。通过修正地形陡峭指数(R)对滑坡型和冲蚀型泥石流进行了有效区分,区分两种坡面泥石流的阈值为R=4。本研究结果有助于深入研究坡面泥石流的地形条件以及流动性特征。

Slope debris flow commonly originates from the mass failures on steep terrain,which has the characteristics of wide distribution and large quantity.In order to distinguish the types of landslide-type and erosion-type slope debris flow,in this work,the grain component and morphological characteristics of the two types of slope debris flows were analyzed by field investigation and UAV method.The ruggedness number,together with fan gradient,length of flow path and mobility index,is used to analyze the mobility characteristics of the two flows,and then modified it.The results show that the erosion-type slope debris flow deposits slope mainly consists of coarse particles,while the landslide-type slope debris flow deposits are composed of fine particles.The depositional fan of erosion-type debris flow is steeper than that of landslide-type,while the mobility is slightly weaker.A new index,equaling to the product of ruggedness number and wide ratio,is propose to distinguish the tow flow types by the threshold of R=4.The results of this work can be helpful for further knowledge about the topography and mobility of slope debris flow.