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西北地区干旱少雨,但却在新疆天山、阿尔泰山及东西准噶尔盆地等硬质岩裸露地区频繁暴发泥石流,究其原因与粗粒花岗岩自身易遭到物理风化有关。以哈密市天山故乡河流域三道沟左岸黑石沟花岗岩裸露地区为例,黑石沟特殊的地形条件(高差大、沟床比降大、沟道内存在两级高度6~8m的跌水坎)、粗粒(粒径达0.5~2.0mm)花岗岩易温差风化及夏季(6~8月)降水集中、降雨历时较短、降雨强度大是形成泥石流的充分必要条件。根据泥痕断面法和雨洪法判断历史上黑石沟内曾暴发多期泥石流,重点探讨了最为显著的两期泥石流侵蚀、输移、堆积的活动特点及泥石流堆积物粒度特征及流体性质,发现该沟泥石流为典型的低频稀性水石流,潜在危害性大,应采取防治措施。
In the northwestern part of China, arid areas are drier, but debris flows frequently occur in the bare areas of the Tianshan Mountains, the Altai Mountains and the East-West Junggar Basin in Xinjiang. The reason for this is that the coarse-grained granites are susceptible to physical weathering. Taking the exposed area of Heishigou granite in the left bank of Sandaogou, the hometown of Tianshan, Hami, as an example, the special topographic conditions of Blackstone ditch (large height difference and large ditch bed ratio, there are two levels of water horizons of 6 ~ 8m in the channel) , Coarse grain (0.5 ~ 2.0mm) granite easily weathering and precipitation (6 ~ August) concentrated precipitation, rainfall duration is short, rainfall intensity is sufficient and necessary conditions for the formation of debris flow. Based on the mud scar cross section method and rain flood method, the historical debris flow in the Hei Ditch ditch has been judged. The most prominent characteristics of erosion, transport and accumulation in the two debris flows and particle size characteristics and fluid properties of the debris flow deposit are discussed. The gully debris flow is a typical low-frequency dilute water stone flow, potentially harmful, should take prevention and treatment measures.