【作者】 张娟娟；

【导师】 杨方社；

【作者基本信息】 西北大学 ， 环境工程（专业学位）， 2015， 硕士

【摘要】 位于晋、陕、蒙交界区域的砒砂岩区,是我国黄河中游粗沙多沙区的核心产沙区,该区域面积约有1.2万km2,占黄河中游整个粗沙多沙区面积的7.6%,但其产沙粗沙量却占整个入黄粗沙量的20-30%,加之该区域水土流失异常严重,成为入黄粗沙的主要来源之一。实践证明,植物是治理水土流失的根本措施。已有研究表明,沙棘植物是治理砒砂岩区沟道水土流失的先锋树种,沙棘柔性坝是治理砒砂岩沟道水土流失的一种有效的生态措施,可将泥沙就地拦截在沟道里,进一步减轻黄河下游粗泥沙淤积。2013年9月,在陕西眉县建立了西北大学沙棘柔性坝野外试验基地,开展了恒定流条件下,沙棘柔性坝在不同生长期(5月和9月),对水流特性的影响试验,为进一步探讨沙棘柔性坝拦沙机理奠定基础和积累数据,以便为沙棘柔性坝在砒砂岩区支毛沟道内的广泛栽植提供理论与实践依据。本文根据水力学及河流动力学的基本理论,对流经沙棘柔性坝内水流的特性进行了分析,并对沙棘植物阻力特性进行了简单探讨。本次试验修正了以往沙棘柔性坝野外试验的一些不足,主要表现在：完善了野外试验设施,修建了5个试验床,其中4个床布置了种植参数不同的沙棘柔性坝,另1个空白对比试验床；在进水口前建有矩形量水堰,实现了对进口流量的实时观测；本试验运用Z L Y—Ⅰ型智能流速仪,通过联机软件可实现对流速精确测量；基于试验数据,本文主要对沙棘柔性坝坝内的水深及流速的纵横向分布与变化进行了分析。所得结果与主要结论如下：(1)分析了沙棘柔性坝的株距、坝长、柔性坝床面坡度和植物生长等对水深的影响,发现坝长是柔性坝水深增加的主要影响因子,通过对试验结果的比较,初步优选出4#坝型。(2)通过分析沙棘柔性坝内不同条件下水深纵向沿程变化,发现沙棘柔性坝试验床内的水深与空白对比床的水深有明显不同,沙棘柔性坝坝前段和上游区壅水相当明显,表明沙棘柔性坝具有显著的阻水效应。(3)在不同工况、不同坝型条件下,分析了沙棘柔性坝内流速纵向沿程变化、横断面流速分布与变化。流速纵向沿程变化为沙棘柔性坝坝前段和上游壅水区流速明显降低,而水流出沙棘柔性坝后,即在沙棘柔性坝坝尾处,流速骤升；通过分析横断面流速分布与变化,发现1#～4#坝与5#空白床的横断面流速分布显著不同,结果表明,1#～4#沙棘柔性坝对水流有较强的阻滞作用。(4)运用河流动力学基本理论,在前人研究的基础上,探讨了沙棘植物的阻力、阻力系数、总边界阻力及糙率系数的计算公式。阻力系数计算公式表明,水流的阻力系数与沙棘柔性坝坝长、坝宽及坡度密切相关；糙率系数计算公式表明,沙棘柔性坝糙率系数与沟床平均种植密度及水力半径呈现出一定的正相关关系,与淹没体积比成反相关的关系。更多还原

【Abstract】 The arsenic sandstone areas that located in the border area of Jin, Shan and Meng is the core of our country more coarse sand sand area in the middle reaches of the Yellow River sand production, covers an area of about 12000 square kilometers, the region accounted for 7.6% of the more coarse sand sand area in the middle reaches of the Yellow River area, but its amount with abundant and coarse sediment yield is 20～30% of the total into the yellow coarse sand content, combined with the abnormal severe soil erosion area, become one of the main sources to the yellow coarse sand.Practice has proved that the plant is the basic measures to control soil erosion. Existing research shows that the seabuckthorn plant is governance arsenic channel of pioneer species, soil and water loss in the zone of the seabuckthorn flexible dam is governance arsenic sandstone channel an effective ecological measures of soil erosion, sediment in situ can be intercepted in the channel, to further reduce the coarse sediment deposition on the lower reaches of the Yellow River. In the July,2013, established the new seabuckthorn flexible dam field test site in Meixian,Shanxi Province. Carried out under the condition of constant flow the influence of the seabuckthorn flexible dam on water flow characteristics test in different growth periods(May and September).In order to further explore the seabuckthorn flexible dam block foundation and accumulated data, for the seabuckthorn flexible dam in arsenic sandstone areas widely planted within the branch channel to provide the theory and practice basis.In this paper, according to the basic theory of hydraulics and river dynamics, within the seabuckthorn flexible dam on water flow characteristics are analyzed, and the resistance characteristics of seabuckthorn plant has carried on the simple discussion. The test fixed field experiment of the seabuckthom flexible dam before some shortcomings, mainly displays in:perfecting the field test facilities, constructed of the five test bed, setting up four bed planting different parameters of the seabuckthorn flexible dam, a blank contrast test bed, replacing the previous blank contrast in the front of the dam section in field test bed; A rectangular measuring weir in above water inlet realizes the real-time observation of import flow; The success of the experiment instead of PIV velocity measuring method, using ZLY-type I combined intelligent velocity instrument and computer realizes the accurate measurement of hydraulic elements; realizes the control of constant flow’s test conditions in the field’s test site, makeing the constant water flow test from indoor to outdoor;Based on test data, this paper mainly discusses the seabuckthorn flexible dam dam plexus in depth and horizontal distribution of flow velocity and changes are analyzed. The results obtained with the main conclusions are as follows:(1)analysis of the seabuckthorn flexible dam planting distance, long dam, flexible dam bed surface slope and the influence on the depth of the water the plants growth, found long dam is a flexible dam water depth increases the major influence factors, through the comparison of the program, preliminary selected 4 # dam type.(2)Based on the analysis of the seabuckthom flexible dam under the condition of different water depth of vertical variation along the river, found within the test bed of seabuckthom flexible dam water depth compared with blank bed depth are obviously different, seabuckthorn flexible dam, dam, the first and the upstream area of backwater is quite obvious, suggests that the seabuckthorn flexible dam has significant effect of block water.(3)Under the condition of different working conditions, and different type of dam, analyzed the seabuckthorn flexible dam longitudinal and cross sectional velocity distribution along the change in velocity and change. Vertical flow velocity along the change for the seabuckthorn flexible dam dam upstream velocity decrease backwater area, the first and the water flow out of the seabuckthorn flexible dam, namely in the seabuckthorn flexible dam dam at the end, flow surge; Through the analysis of cross sectional velocity distribution and change, found the 1#～4# dam and 5# empty bed cross-sectional velocity distribution curves in different, the 1#～4# dam the flow regime, changes in the opposite direction, velocity curves in roughly the parabolic shape distribution, center of the river flow velocity less than the flow of the river bed wall, blocking effects of seabuckthorn flexible dam on water flow.(4)With the basic theory of river dynamics, on the basis of predecessors’ research, discusses the seabuckthorn plant resistance, resistance coefficient, total boundary resistance and roughness coefficient calculation formula. Drag coefficient formula shows that the flow resistance coefficient and the seabuckthorn flexible dam dam, dam width and slope is closely related to the long; Formula of roughness coefficient, seabuckthorn flexible dam is average roughness coefficient and gully bed planting density and hydraulic radius presents certain positive correlation, related to flood volume into the relationship.更多还原