新疆黑石沟花岗岩裸露区历史泥石流形成条件及活动特点

Formation Condition and Activity Characteristics of Debris Flow for Coarse Grained Granite of Ragstone in Xinjiang

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。

Because coarse-grained granite is vulnerable to strong physical weathering in arid zone, debris flow is fre- quent outbreaks in ragstone exposed areas such as Tien Shah, Altai Mountains and eastern and western of Junggar basin of Xinjiang. This article studies the debris flow of Heishigou which is on the left bank of Sandaogou in Shichenzi valley where plenty of granite exposed. The results show that abundant collapse which formed by strong physical weathering of ragstone in long-term arid environment and tectonic activity were regarded as the main loose material source of occurrence of debris flow disasters~ watershed topography of narrow valleys, large grade and concentrated heavy rainfall formed the necessary and sufficient condition. Due to the strongly deep-cutting erosion of debris flow, the phenomenon such as drop water dams, bedrock valley and bottom corrosion are obvious in the valley. Using dirt mark section method and rainstorm flood method, we find out that Heishigou outbroke of several debris flows. This paper focuses two significant periods of debris flow on activity characteristics of erosion, transport and deposition. We draw a conclusion that Heishigou is a typi- cal low-frequency diluent water stone debris flow and has a strong potential hazard. Therefore, some measures should be taken to nrevent debris flow.