冰碛湖溃决泥石流流量计算方法

Computing method for discharges of debris flow induced by moraine-dammed lake outburst

冰碛湖溃决泥石流是高山高寒地区一种常见的灾害类型,虽爆发频率低,但造成的危害极大,该类型的泥石流防治是区域开发建设中必须要面对的问题,而流量计算又是其核心问题之一。以西藏地区近100 a以来的冰碛湖溃决实例为基础,探讨了溃口深度的计算方法;以逐渐溃决模型和配方法为基础,分析了冰碛湖溃决泥石流的容重峰值流量与洪峰演进计算方法的适用性与流程;通过案例的对比研究,探讨了计算模型参数率定与误差来源。结果表明:瞬间溃决模型高估了冰碛湖溃决泥石流的峰值流量,泥石流的预测值偏保守;而逐渐溃决模型更接近于冰碛湖溃决的物理机制,在冰川U型谷内,可不考虑泥石流的堵塞作用,泥石流的峰值流量预测值与实测值较吻合;在冰川U型谷外或近沟口段则需考虑泥石流的堵塞作用。文中提出的计算模型作为冰碛湖溃决泥石流防治工程参数设计的依据是可行的。

The debris flow induced by moraine-dammed lake outburst, characterized by low frequency as well as incredible perniciousness, is one of the common geo-hazards in alpine regions with vulnerable environment. Challenges of hazard mitigation, especially the key issues with discharge design, have to be dealt with in the process of regional development and construction. Based on case studies of moraine dammed lakes in the recent 100 years in Tibet, the variation of breach depth of terminal moraine-dammed dam is analyzed;on the basis of gradual breach model and flood-deposition mixture method, computing methods and procedures for unit weight, peak discharge and flood routing of debris flow mobilized by moraine-dammed lake outburst flood are discussed herein. The parameter calibrations and error sources of various computing models are discussed by means of comparative study among relative cases. It is indicated that the gradual outburst model typically overestimate the peak discharges of debris flow and the predicted parameters tend to be conservative;the gradual outburst model, however, substantially coincide with the physical mechanisms of moraine-dammed lake outburst;the predicted peak discharges of debris flow surging in the U shape gully, in which the plugging effect could be negligible, are in line with field investigation by and large. However, the plugging effect could be significant and can not be negligible outside the U shape gully or near the channel mouth. Therefore, the method put forward herein is generally feasible for parameter designs of debris flow control project.