强震区典型窄陡沟道型泥石流发育特征

针对汶川强震区5条典型窄陡沟道型泥石流进行实地勘察。通过室内颗分试验、激光衍射粒度分析试验、X射线衍射试验,分析了强震区窄陡沟道型泥石流的基本发育特征、堆积物颗粒级配和黏土矿物定量组成。结果表明：(1)强震区窄陡沟道型泥石流典型发育特征除了地形地貌上的“窄”和“陡”外,震后松散物源量中崩滑物源和沟道堆积物源显著增多,动储量比例增大,造成强震区窄陡沟道型泥石流危险性显著提高。(2)强震区窄陡沟道型泥石流堆积物固体颗粒级配分布范围较广,连续性较好。级配曲线不均匀系数均大于5,曲率系数在0.95~3之间,无缺失粒组;粒径小于0.075mm的粉粒含量均在0.5%以下,粒径小于0.005mm黏粒含量均在0.11%以下,不同沟道间差别较小。(3)强震区窄陡沟道型泥石流堆积物黏土矿物主要由伊利石、绿泥石和伊蒙混层三种黏土矿物组成,各自含量平均值分别为45.6%、38.8%、15.6%。伊利石和绿泥石总含量均超过75%,伊蒙混层含量均在25%以下。开展汶川强震区的典型窄沟型泥石流发育特征分析,对于地质灾害泥石流风险评估、监测预警和防控具有重要意义。

Development Characteristics of Typical Narrow-Steep Gully Debris Flow in Seizoseismal Area

Five typical narrow-steep gully debris flows were field investigated in Wenchuan meizoseismal area. The basic development characteristics, particle size distribution of deposits and quantitative composition of clay minerals of narrow-steep gully debris flow in meizoseismal area were analyzed through particle size distribution test, laser diffraction particle size analysis test and X-ray diffraction test. The results show that: (1) In addition to the "narrow" and "steep" in topography and geomorphology, the typical development characteristics of narrow-steep channel debris flow in meizoseismal area are that the sources of landslides and channel deposits increase significantly after earthquake and the proportion of dynamic reserves increases, resulting in a significant increase in risk. (2) The distribution of solid particles in debris flow deposits has a wide distribution range and good continuity. The unifornity coefficients of all gradation curves are greater than 5, and curvature coefficient between 0.95 and 3. The particle size less than 0.075mm powder content is below 0.5% and the particle size less than 0.005mm sticky content is below 0.11%, with small differences between the different trenches. (3) The clay minerals in the deposit are mainly composed of illite, chlorite and illite smectite mixed layer, with average contents of 45.60%, 38.80% and 15.60% respectively.The total content of illite and chlorite is more than 75%, and the content of illite smectite mixed layer is less than 25%. It is of great significance to analyze the development characteristics of typical narrow-steep gully debris flow in Wenchuan meizoseismal area for risk assessment, monitoring, early warning, prevention and control.