箱体消能式泥石流排导槽排导特性研究

The erosion and abrasion damage is easily appeared in the Dongchuan debris flow channel and V-shaped drainage canal for discharging the debris flow in the drainage canal with large longitudinal slope (0.15<i<0.50) in the small watershed. In order to deal with this issue, a drainage canal with energy dissipation cabinet was proposed and it can be used to discharge the debris flow in a small watershed with large longitudinal slope. Although this kind of drainage canal has applied successfully for practical disaster prevention and mitigation engineering, the motion characteristics of debris flow and the effect of energy dissipation cabinet still is lack of theoretical research. Therefore, it is difficult to calculate the accurate parameters and it is more difficult to expect that this new type drainage canal can meet the requirement of the popularization and application in the prevention and mitigation engineering. This study was carried out on the debris flow drainage canal with energy dissipation cabinet in the small watershed with large longitudinal slope by using the way of theoretical research, model tests and numerical simulation. Simultaneously, much emphasis was put on the research content of the motion characteristics of debris flow in the drainage canal and variation law of energy dissipation ratio. Furthermore, In order to obtain the variation law of energy dissipation ratio and get a complete research result on the debris flow drainage canal with energy dissipation cabinet (Mechanism research -parameters determination-parameter optimization-promote the application), the detailed analysis was carried out on the results of model tests and numerical simulation. Therefore, the research results can provide reference for optimizing the design of this new type of drainage canal and it has the great significance to improve the techniques level and enlarge the application range of mitigation engineering.

针对软基消能型或全衬砌型排导槽在排导沟床纵比降很大(0.15<i<0.50)的泥石流过程中易导致排导槽冲刷磨蚀破坏的问题，本项目拟采用理论分析、模型实验和数值模拟相结合的方法对适用于排导沟床纵比降很大的小流域泥石流的箱体消能式泥石流排导槽开展研究,重点对泥石流在排导槽内的运动特性，排导槽纵比降、箱体长度、宽度、高度等与箱体段消能率之间的变化规律等内容进行详细研究，通过分析泥石流在箱体消能式泥石流排导槽内的运动特征、泥石流与箱体相互作用机制，获得排导槽纵比降、箱体长度、宽度和高度等与箱体段消能率之间的变化规律及箱体参数的优化设计方法。本项目从作用机理、关键参数确定，参数优化设计等方面开展研究，以期获得一套完整的"机理研究-参数确定-参数优化"的箱体消能式泥石流排导槽研究成果。本研究可为箱体消能式泥石流排导槽优化设计提供参考和依据，对提高泥石流防治技术水平及新型排导槽的推广应用具有重要意义。

针对汶川地震和芦山地震后面临的泥石流排导问题，通过野外调查对地震灾区修建的排导槽工程进行调查获取数据，通过系列的模型实验对箱体消能式泥石流排导槽的泥石流运动流态、流速变化规律、消能机理和消能率等开展研究。通过大量的野外调查工作，总结了现存的泥石流防治工程主要存在的问题：排导槽未设置弯道超高、排导槽严重冲刷破坏、排导槽排导不畅。在中国科学院东川泥石流观测研究开展了坡度为15%、20%、25%、30%和35%条件下的排导槽模型实验（约200组）。实验结果表明：.(1) 泥石流运动流态：当箱体槽坡度不变，而箱体宽度逐渐减小过程中，参与消能的箱体面积减小，箱体两侧的泥石流呈现出光滑流态，箱体段两侧的泥石流运动流速大于中部流速，而箱体段两侧的泥深小于排导中部的泥深；.(2) 箱体消能结构段下游泥深特性：箱体消能结构下游的泥深随着箱体消能段长度的增加而逐渐增大，箱体消能结构宽度较大时泥深增大较为明显。当排导稀性泥石流时，随着箱体消能结构宽度的变化，箱体消能结构段下游的泥深约为同一位置光滑水槽泥深的（2.1-3.1）倍，约为整个箱体消能槽平均泥深的（1.6-2.4）倍；当排导粘性泥石流时，随着箱体消能结构宽度的变化，箱体消能结构段下游的泥深约为同一位置光滑水槽泥深的（1.7-2.1）倍；.(3) 箱体消能结构段下游流速特性：无论是排导稀性泥石流还是粘性泥石流情况下，箱体消能结构段下游的平均流速均随着箱体消能结构段长度的增加而逐渐减小、随着排导槽坡度的增加而逐渐增大。箱体消能式排导槽出口断面泥石流平均流速约为光滑排导槽出口断面流速的（0.53-0.55）倍；.(4) 箱体消能槽消能特性：无论是排导稀性泥石流还是粘性泥石流情况下，箱体消能结构段的消能率均随着箱体消能结构段长度、宽度的增加而逐渐增加。当排导稀性泥石流时，消能率随着排导槽坡度的增加而逐渐增大，最大值为67%；排导粘性泥石流时，消能率随着排导槽坡度的增加先逐渐增大然后逐渐减小，在排导槽坡度为25%时，达到一个最大值为69%。