IMHE OpenIR  > 山地灾害与地表过程重点实验室
泥石流排导槽消能体流速调控机理及应用研究
Alternative TitleResearch on the mechanism of debris-flow velocity control and Application of Eenrgy dissipation structure in a Drainage Channel
王飞
Subtype博士
Thesis Advisor陈晓清
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline岩土工程
Keyword泥石流 消能体 水槽试验 数值模拟 消能机理
Abstract泥石流是山区常见的地质灾害之一,是制约山区经济发展及人民财产安全的重要因素。泥石流通常会携带大量泥沙或块石,对沟道下游道路、桥梁、房屋、工厂等基础设施造成严重的淤埋碰撞威胁。此外,冲击磨蚀较强的泥石流也会对泥石流防治工程造成较大的威胁,影响工程整体治理效果。排导槽是泥石流顺利通过保护区域的主要工程措施,但泥石流的磨蚀作用会对排导槽底部造成严重的损坏,特别是公路沿线大比降排导槽。例如绵茂汉清公路段小岗剑泥石流排导槽比降达到34%,每次发生泥石流都会对排导槽造成很大的磨蚀,增大了工程后续维护投入。通过在排导槽中布置多排消能体,增加泥石流与消能体之间的碰撞作用,可以增大摩擦、混掺消能,降低泥石流流速及水槽底部流速,从而降低了排导槽底部的磨蚀作用。现阶段泥石流与消能体的混掺消能机理尚未完全揭示,特别是泥石流浆体及其中块石对排导槽的磨蚀作用。本文通过研究泥石流容重、水槽纵坡、消能体排间距及形状对减速率、运动形态的影响,可为消能体工程设计提供参考。目前取得的研究成果如下:1. 通过开展泥石流与消能体的模型试验,得到泥石流通过消能体的基本运动形态,并通过理论计算得到了泥石流的挑流公式根据水槽试验现象进行分析,得到泥石流通过消能体时泥深增大,呈纵向扩散;在与交错布置的消能体作用发生碰撞时,泥石流在平面上被分为多股,与消能体相互碰撞,促进了能量消耗,降低了泥石流流速。通过泥石流挑流高度与容重对比发现,泥石流容重越大粘滞性越强,挑流高度及沿水槽的运动距离越小;容重越小粘滞性越小,通过消能体时流体容易发生飞溅,挑流高度及沿水槽距离越大。2. 通过水槽试验得到泥石流容重、水槽纵坡比降、消能体排间距及形状对减速率的影响泥石流减速率与各影响因素之间的关系如下:(1)根据试验结果,同一坡度条件下,减速率有随着容重增大而增加的趋势,通过数据拟合建立了不同坡度条件下减速率与容重的关系式为:9°:n = -9.400 + 1.430γ;12°:n = 13.180 + 0.400γ;15°:n = -1.811 + 1.315γ。(2)消能体排间距对减速率的影响体现在相邻排之间加速过程。随着消能体排间距的增大,泥石流又会重新在重力作用下加速,整体减速率则会降低。随着排间距增大,减速率有逐步减小的趋势,两者的关系式为:9°:n = 15.79 - 10.12L;12°:n = 24.98 - 26.8L;15°:n = 20.95 - 2.814L。(3)消能体通过正面碰撞与混掺作用降低泥石流的能量,消能体外观特征会影响减速的效率。根据对照试验可知,正方体、梯形体及三棱柱消能体的相对减速率范围依次为:9°:10.37~25.94%,11.45~24.05%,14.50~24.85%;12°:28.45~36.03%,34.00~36.69%,28.90~34.25%;15°:28.03~41.31%,36.00~43.82%,30.00~42.50%。(4)水槽坡度会影响泥石流的运动速度。根据拟合方程可知减速率有随着坡度增大而增加的趋势,正方体、梯形体及三棱柱消能体坡度与减速率的拟合方程为:正方体:n = 2.191 + 1.241θ;梯形体:n = 6.369 + 1.016θ;三棱柱:n = 6.021 + 1.062θ。3. 通过数值模拟方法研究了泥石流通过消能体的流速分布、压强分布及形状、排间距对流速的影响数值模拟结果表明泥石流通过消能体时发生纵向扩散,内部形成空腔,与试验现象基本一致;泥石流与消能体作用时流体压强会增大,其中第一排消能体前部压强较大。此外,流体纵向扩散跌落后也会在水槽底部产生较大的压强。泥石流通过交错设置的消能体时流速逐步减小,在第二排消能体前断面平均流速达到最低值。随着交错布置的消能体排间距逐步增大,流体在相邻排之间加速,减速效果也随之越小。流体通过第三排消能体后流速达到最大值,当流体纵向扩散跌落后速度会骤减,此后又会逐步加速。4. 针对多组消能体进行数值模拟研究,提出大比降排导槽多组消能体的设计方法根据模拟结果可知,布置多组消能体的排导槽可以相对减少流体在排导槽中的平均流速,从而达到减小排导槽底部冲刷速度、延长排导槽使用年限的目的;布置消能体情况下平均泥深随着水平位移增大呈现出“增大-减小”交替的波动方式;根据计算得到了多组消能体设计的基本流程、方法,为大比降泥石流排导槽消能体设计提供参考。
Other AbstractDebris flow is one of the common geological disasters in mountainous areas, which is the key restricting factor for economic development and property safety. Debris flow often carries a large amount of sand or rocks, which can cause great threaten to infrastructures at downstream such as roads, bridges, houses and factories. In addition, the strong impact and abrasion of debris flow can lead to a great threaten to debris flow mitigation engineering and influence the overall prevention effect. Debris flow drainage channel is the main engineering control measure, but the bottom of the channel can be serious damaged by debris flow especially that located along the road. For example, the gradient reaches 34% for Xiaogangjian debris flow drainage channel at mianmao-hanqing road. The great erosion of drainage channel after each debris flow can increase the follow-up investment of the project. In order to decrease the erosion of the bottom of the channel, several rows of deceleration bodies were installed in the channel to increase the energy dissipation and the average velocity of debris flow. The interaction mechanism between debris flow and the energy dissipation bodies has not yet been fully revealed, particularly the influence of debris flow and rock for the erosion of drainage channel bottom.In this study, the deceleration ratios and flow pattern have been studied. The influential variables include debris flow density, flume slope, row spacing between adjacent rows and shape of energy dissipation bodies. The result drawn from the research can provide useful references for the design of energy dissipation bodies.1. By conducting the interaction experiment of debris flow and the energy dissipation bodies, we can obtain the basic movement pattern and the deflecting flow formula when debris flow moves through the energy dissipation bodies.By analyzing the result of the flume experiment, it can be found that the debris-flow depth increased and present a longitudinal diffusion in the flume when it went through the energy dissipation bodies. Debris flow has been divided into several parts when it impact with the energy dissipation bodies. The collision between the flows can promote the reduction of the velocity and energy dissipation.By comparing the correlation of the trajectory height and debris flow density, it can be found that the height and the distance of viscous debris flow are smaller than that of dilute debris flow. Dilute debris flow is more likely to splash into the air and has a longer longitudinal diffusion distance.2. The influence of debris-flow density, channel slope, row spacing and shapes of energy dissipation bodies for velocity reduction ratio is obtained by flume experiment.Debris flow reduction rate and the relationship between various influencing factors as follows:(1)According to the experiment result, the velocity reduction ratio is increasing with the increase of debris-flow density at the same channel slope. The relationships are as follows:9°: n = -9.400 + 1.430γ;12°: n = 13.180 + 0.400γ;15°: n = -1.811 + 1.315γ。(2)The spacing between adjacent row of energy dissipation bodies can influence the acceleration process of debris flow. When the spacing increased, the debris-flow velocity accelerated again and the velocity reduction ratio will go down and vice versa. The relations between the two are as follows:9°: n = 15.79 - 10.12L;12°: n = 24.98 - 26.8L;15°: n = 20.95 - 2.814L.(3)The deceleration energy dissipation bodies can reduce the energy by front collision and the interaction with the debris flow. The appearance characteristics will affect the efficiency of the reduction of debris flow. According to the contrast test, the relative reduction ratio of scope for cubes, trapezoidal and triangular prism energy dissipation bodies are as follows in order:9°: 10.37~25.94%, 11.45~24.05%, 14.50~24.85%;12°: 28.45~36.03%, 34.00~36.69%, 28.90~34.25%;15°: 28.03~41.31%, 36.00~43.82%, 30.00~42.50%.(4)The flume slope will affect the speed of debris flow movement. According to the fitting equations of velocity reduction rate and the slope for cubic, trapezoidal and triangular prism energy dissipation structure, the velocity reduction rate is proportional to the the flume slope. The fitting equations of cubic, trapezoidal and triangular prism energy dissipation structure are as follows:Cube: n = 2.191 + 1.241θ;Trapezoid body: n = 6.369 + 1.016θ;Triangular prism: n = 6.021 + 1.062θ.3. The velocity distribution, pressure distribution and the influence of shape and row spacing for velocity reduction rate were studied by numerical simulation method.The numerical simulation analysis shows that longitudinal diffusion and internal cavity occur when debris flow flows through the energy dissipation bodies. The numerical simulation results agree with the experiment phenomenon. The pressure will increase when debris flow encounter with the energy dissipation bodies. The upper side of the first row of energy dissipation body has the maximum pressure. In addition, the longitudinal diffusion of debris flow will lead to a relatively large pressure at the bottom of the flume. The velocity of debris flow will reduce gradually when meet with the energy dissipation body and it will reach its maximum in the second row of the energy dissipation body. With the increase of row spacing, the acceleration effect of debris flow will reduce. The velocity of debris flow will reach the maximum when it went through the third row of energy dissipation body. The velocity will reduce when the debris flow meet the bottom of the flume after the longitudinal diffusion and it will accelerate then gradually.4. Numerical simulation research was conducted to study multi-row energy dissipation body and then come up with the design method of multi-row energy dissipation body for large gradient debris-flow drainage channels.Compared with the channel without energy dissipation bodies, the velocity can be relatively reduced by the arrangement of several sets of energy dissipation bodied. The scouring velocity of the bottom is also reduced, which can prolong the using time of the debris-flow drainage channel. Debris-flow velocity presents the volatility way of "increase and decrease" with the channel bottom arranged with energy dissipation bodies. Moreover, the design procedure and method drawn from the research provide reference for the installment of energy dissipation bodied in a large gradient drainage channel.
Pages112
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24592
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
王飞. 泥石流排导槽消能体流速调控机理及应用研究[D]. 北京. 中国科学院大学,2017.
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