泥石流直墙V型排导槽横断面优化设计

The Optimum Cross-section Design on the "V" Shaped Drainage Canal of Debris Flow

排导槽横断面的形状及尺寸是泥石流排导槽设计的重要参数,如何合理选择过流断面的形状和尺寸,使泥石流排导槽具有最佳的排泄能力,目前国内外的研究还比较少涉及。直墙V型断面排导槽是目前泥石流防治工程中广泛采用的横断面形状之一,以其为研究对象,对它的水力条件进行了分析,并对横断面的优化设计进行了探讨。泥石流排导槽的断面形态系数(M)定义为湿周(P)与水力半径(R)之比,直墙V型排导槽水力最佳时相应的断面形态参数M=[8(1+m2V)1/2-4]/mV,直墙"V"型排导槽水力条件最佳时的断面形态参数M仅与槽底横坡系数有关。假定在已知泥石流直墙V型排导槽排泄流量Q、槽底纵比降I以及泥石流体颗粒级配特征的条件下,推导出了联合求解最优水力条件下直墙V型槽断面形态尺寸的组合公式,并以大渡河上游左岸的一级支沟把丫沟为例,对该沟的泥石流排导槽横断面进行了优化设计。

The drainage canal is one of the most widely-used engineering measures in preventing debris flow. The shape and size of cross-section are important parameters for designing the drainage canal of debris flow. While how to choose optimum shape and size to make the drainage canal of debris flow have the best discharging ability is a problem few people have researched both at home and abroad. The ＂V＂ shape drainage canal is one of widely-used cross-section shapes for the preventing engineering of debris flow. This paper chooses it as researching object, analyzes its hydraulic condition, and discusses its optimum cross-section design. The cross-section configuration parameter of ＂V＂ shape debris flow drainage canal （M） is defined as the ratio of wetted perimeter （P） to hydraulic radius（R）. Based on the definition, the cross-section configuration parameter of ＂V＂ shape debris flow drainage canal （M） is deduced as M =[ 8 （1＋m^V^2）^1/2-4]/mV under the optimal hydraulic condition. By analyzing the optimal hydraulic condition, it is indicated that M decreases with the increase of, or the more optimal hydraulic condition of the ＂V＂ shape debris flow drainage canal with the increase of. When is between to infinite, M increases with increase of or the worse hydraulic condition of the ＂V＂ shape debris flow drainage canal with the increase of. When is equal to, M is minimum and equal to 6.93. The discharge of debris flow （Q） , the longitudinal gradient of debris flow drainage canal （I） and the gradation of debris flow grain are assumed as known. After simultaneous numerical solution, the combinatorial calculating formulas of the cross-section size of ＂V＂ shaped debris flow drainage canal are obtained. On the basis of the analysis of the optimal hydraulic condition of ＂V＂ shaped debris flow drainage canal, this paper takes the prevention engineering design of Bayahe Gully as an example for optimum cross-section design of debris flow drainage canal. After calculation, the width and the depth of the debris flow drainage ca- nal in Bayahe Gully are equal to 17.86 m, 6.97 m respectively.