三眼峪特大泥石流形成的物源条件分析

Analysis of Material Sources Derived from Sanyanyu Debris Flow in Zhouqu County

通过对舟曲县"8.8"特大山洪泥石流三眼峪沟进行现场调查,从泥石流的岩土体类型及特征、地质构造、水文地质、新构造运动及地震等方面,对物源条件的地质环境背景进行了总结。调查结果表明:①三眼峪沟泥石流的松散固体物质主要包括崩塌堆积物、滑坡堆积物、残坡积物和冲洪积物。②三眼峪沟松散固体物质总量4 079.42×104m3,流域内可转化为泥石流的松散固体物质总量为2 644.54×104m3,占总量的64.8%。③三眼峪沟流域固体松散物质转化为泥石流组成部分的主要方式包括崩塌、滑坡直接堆积或堵塞沟道,被水流冲蚀、搬运;沟坡上的残坡积物、滑坡体、崩塌体表层在雨水面蚀作用下,细粒物质流入沟道,补给泥石流,增加了泥石流的黏度;沟道内的早期泥石流停积物直接被冲蚀、搬运,构成泥石流固体物质等。

Through the field investigation of Sanyanyu Valley in Zhouqu county where occurred the giant flush flood and debris flow on August 8, 2010, the author summarized the geological environment background of loose solid material sources from several aspects of topography, stratum lithology, geological structure, hydrological geology, new tectonic movement and earthquake. Investigation results show that： ①The loose solid matter of Sanyanyu debris flow mainly include collapse deposit, landslide deposit, eluvial deposit, talus deposit and trench deposit. ①The total volume of loose solid matter of Sanyanyu valley is about 40 794 200 m^3, which can convert to debris flow nearly 26 445 400 m^3 （64. 8%）. ③The fundamental mode of Sanyanyu Gully loose mass converted to the components of debris flow included collapse and landslide deposited directly or fluvial eroded and transported by jamming trench; The fine grain material of gully slope＇s remnant slope sediment, the landside mass, the collapse body flowed into the trench under the rainfall＇s surface erosion function, supplied the debris flow and increased its viscosity; The early debris flow deposit in trench was eroded and transported directly, constituted the debris flow mass.