泥石流堵塞大河的特点及异岸受灾判据研究

研究了典型堵河事件,提出了泥石流堵塞大河的特点:存在全堵、壅堵和局部堵塞3种堵河模式;局部堵塞是最普遍的堵河形式;高速水流冲刷异岸,或迫使主河改道而成灾是泥石流局部堵塞大河的主要成灾模式之一。针对这种成灾模式运用数值模拟方法分析主河在不同堵塞系数时的水流流场,基于信息熵原理分析主河流场有序度,得出当堵塞系数R为0.80～0.90时,主河流场熵值急剧下降,且此时流速也大,把堵塞系数R>0.80作为泥石流局部堵河异岸受灾判据。通过岷江流域银杏至映秀段泥石流堵河实例验证,表明数值模拟结果与实际情况吻合,泥石流局部堵河异岸受灾判据可行,为制定泥石流堵河灾害减灾对策提供科学依据。

Study on Features of River-blocked by Debris Flow and Criterion of Disaster at the Opposite River Bank

The frequency and damage of the natural disasters, especially the mountain disasters, have increased significantly in recent years. There were lots of debris flows blocking large river cases. This paper studies the typical river-blocked case. The characteristics of the river-blocked by debris flow were proposed. There are three river-blocked types: entire block, obstruct block, and local block. The frequency and damage of the natural disasters, especially the mountain disasters, have increased significantly in recent years. There are lots of the events of debris flows blocking great rivers. This paper studies the typical river-blocked case. The features of the river-blocked by debris flow are proposed. There are three river-blocked types: total blocking, obstruct blocking, and local blocking. The local blocking is the most widespread type. One of the disaster modes caused by the local blocking is the river diversion due to the scouring of the opposite bank by the river flow with high velocity. The flow field of the main river with different block coefficients was analyzed by the numerical simulation method according to this disaster type. The order degree of the main river was studied based on information entropy principle. When the block coefficient R was in the range of 0.8 to 0.9, the entropy of the main river decreased rapidly, and the velocity of the water flow was fast. The block coefficient, R>0.80, was taken as the criterion of the local blocking of the river by the debris flow. Verified by the river-blocked event caused by the debris flow along Minjiang River between Yinxing to Yingxiu section, the results of numerical simulation compared with the field data well. The criterion of the disaster at the opposite bank due to river-blocked caused by the debris flow is validated. The scientific basis is proposed for the development of the countermeasures for the river-blocked disasters caused by the debris flow.