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通过对2013-07-10汶川古溪沟泥石流灾害的现场调查,从物源、地形和水源条件入手,分析了灾害成因与形成演化过程。堰塞体失稳补给、坡面泥石流入汇和沟道侵蚀是这场泥石流的三种物源形式,充沛的前期降雨和短历时强降雨是本次泥石流的诱发因素,陡峻的支沟地形促进了泥石流的加速,沿途松散物质补给,导致泥石流流量不断放大,峰值流量最大可达1 063 m3/s。主支沟泥石流呈明显的阵流特征,原因在于各支沟泥石流起动条件不同,沟道中地形条件的差异和防治工程的分布,以及各支沟汇流长度存在区别。泥石流总规模约为100×104m3,防治工程拦挡了60%的泥石流体,并拦截了泥石流中的大石块,降低了出口峰值流量和流速,同时避免了各条支沟泥石流同时到达而流量激增。沟口泥石流峰值流量约为722 m3/s,约40×104m3泥石流冲出沟口,下游泥石流破坏形式以淤埋破坏为主。本研究可为此类面积较大、修建有防治工程的流域泥石流形成和减灾提供参考。
Based on the site investigation of the debris flow disaster in Guxigou, Wenchuan, from July, 2013 to July, this article analyzes the causes of formation and evolution of the disaster from the aspects of provenance, topography and water source conditions. Weir body instability supply, slope debris flow into the sink and channel erosion is the source of this debris flow three forms, plenty of early rainfall and short duration of heavy rainfall is the predisposing factors of this debris flow, the steep branch terrain promotion The acceleration of debris flows and the supply of loose materials along the route led to the continual amplification of debris flow and the maximum flow rate reached 1,063 m3 / s. Debris flow in the main branch channel shows obvious characteristics of the matrix flow. The reason is that there are differences in the starting conditions of the debris flow in each branch channel, the differences of topographical conditions in the channels and the distribution of prevention and control projects, and the confluence length of each branch channel. The total scale of debris flow is about 100 × 104m3. The prevention and control project blocks 60% of the debris fluid and intercepts the large stones in the debris flow, reducing the peak discharge and flow rate at the exit. At the same time, it avoids the simultaneous surge of flow in each branch of debris flow . Mizobe mudslide peak flow of about 722 m3 / s, about 40 × 104m3 debris flow out of the Mizoguchi, the downstream debris flow to form the main damage to the destruction of silt. This study may provide a reference for the formation and mitigation of such debris flows and landslides in such large area and prevention and control projects.