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考虑流固耦合效应的泥石流作用下拦砂坝动力响应分析
Alternative TitleThe Dynamic Response Analysis of the Slit-trap Dam Under the Action of Debris Flow Based on Fluid-Solid Coupling
Language中文
李昆
Thesis Advisor陈晓清
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name博士
Degree Discipline岩土工程
Keyword切口拦砂坝 等效应力 流固耦合 有限单元法 数值模拟 动力响应
Other Abstract

泥石流是破坏性极其严重的快速地质过程,具有分布范围广,暴发频繁,搬运能力强,成灾率高,危害性大等特点,常常会对山区的人民和财产造成直接严重的破坏和伤害。在泥石流防治工程中,在泥石流形成区或形成—流通区内修建拦砂坝是防治泥石流最快速且非常行之有效的方法之一。在室内水槽实验的基础上,基于流固耦合数值理论,同时考虑泥石流的流变模型,开展了拦砂坝动力响应的研究,详细介绍和完成了拦砂坝在不同泥石流密度、入口流速、坡度条件下单向与双向流固耦合分析,获得两者的相关数据,并将数值模拟结果与实验现象进行比对,结果比较吻合。旨在为坝体设计优选以及周围泥石流流场理论的研究提供科学参考依据。通过分析研究,初步得到如下主要研究成果:(1)在泥石流冲击力作用下,拦砂坝底部压力最大。流固耦合作用随着流速,密度以及坡度的增加而增加,其中流速对流固耦合作用的影响最为显著;坝基的等效应力最大,坝肩的等效应力最小。坝体迎水面变形最先出现在坝基处,变形呈现由中间向两侧扩展特点,扩展特点呈现外扩的环形轮廓,且坝基和溢流口上部变形较为明显。(2) 预测了拦砂坝压力以及泥石流过坝前后的基本流态。在坝体迎水面附近泥石流流速达到最大值,泥石流过坝以后等值线由密逐渐变疏,流速变化由剧烈变为平缓。泥石流在冲击区靠近迎水面坝基的出现压力最高值且在该处的压力梯度最大,过坝后由于受到坝体反向作用力影响流场压强迅速降低,背水面坝肩处从负值压强逐渐增加,负压的存在可能导致泥石流坝后的磨蚀。泥石流在靠近拦砂坝溢流口的附近形成漩涡,结构比较规则,逐渐增强,随后且漩涡中心出现下移渐渐衰弱消失。(3) 坝体在受到冲击初期节点加速度达到最大值,随后随着冲击过程地深入,坝体受到泥石流的冲击慢慢减小,坝体位移开始恢复原状并产生负的位移。通过室内试验获得泥石流在过坝前后的运动特征。稀性泥石流在槽中运动,较细颗粒与水相互作用结合成类似均质浆体,二者不易发生分离,过坝时表层紊动非常强烈。粘性泥石流流在槽中运动过程,龙头很少液相,流动速度与后续流流速相差不大,后部水流携带砾砂作推移质运动,输沙率较大。 (4) 研究动力响应一种抽象的简化模型来分析泥石流与防治结构的相互作用过程,该模型为多自由度的粘弹性模型,并在此基础上推导出防治结构的位移公式:以达朗贝尔原理为基础,将拦砂坝简化为两端固定的梁,将坝体的荷载沿横均匀分布或者按正弦函数分布,忽略坝体横向变形,视泥石流为三维不可压缩的流体。得出坝体位移两个公式: 

;

Debris flow is extremely serious destructive geological process, with wide distribution, frequent outbreaks, strong handling capacity, high disaster and other characteristics, often causing serious damage to people and bring property damage directly in the mountain area. Buliding check-dam in the forming-circulation area is one of the fastest and most effective methods in the debris flow project.Based on the flume experiments and fluid-structure coupling, taking into account the rheological model of mudslides, the research of check dams dynamic response were carried out under the condition of different density, entrance flow rate and slope using both one-way and two-way FSI analysis to obtain the relevant data, and the numerical simulation results agrees well with experimental results. And preferably its aim is to provide scientific reference to study the flow field around the dam and check-dam design. Through analysis, preliminary main research results are obtained as follows: (1) Throughout the fluid region, the biggest pressure appeared at the bottom of check dams. Fluid-structure coupling became stronger with the velocity increasing, density and the slope, of which the flow rate of was the most convection-structure interaction effective factors; The maximum equivalent stress appeared at the dam foundation, while the minimum equivalent stress appeared at the dam abutment. Positive side first appeared at the bottom of the check dam, then the deformation exhibit from the middle to both sides and it was obvious on the overflow dam foundation and at the dam abutment.(2) Predict basic flow patterns before and after passing the dam.In the vicinity of the dam upstream face the debris flow velocity reached maximum, after mudslides passing the contour gradually becamet dense, dramatic change in flow rate became flat. Mudslides in the impact area of the upstream face of the dam and the maximum pressure gradient occurred. After mudslides passing the dam, the negative pressure of the check dam gradually formed and lead to the abrasive of the dam. Vortex formed near the overflow in the vicinity of check dams, with its shape rule, and gradually increased. The vortex then gradually moved downward the center and became weaker and finally disappeared.(3) The node acceleration of the dam reached a maximum, followed by in-depth with the impact process, the displacement of the dam gradually decreased and then began to become negative. The motion feature of debris flow was obtained before and after passing the dam through the laboratory tests. When thin viscous debris flow was moving in the tank movement, finer particles interaction with water, which hardly separate, combined into homogeneous slurry similar. The surface is very strong turbulence when passing the dam. Viscous debris flow was moving in the tank movement with little liquid, of which the flow rate was similar as the following fluid. And rear water carrying sand for gravel bed load motion, and the sediment transport rate was high.(4) The dynamic response of a simplified model was studied to analyze the interaction of debris flow and control structure, the model of multi-degree of freedom viscoelastic model was taken to derive formulas displacement prevention structures:Check dam was supposed to the fixed ends of the beam, of which the dam load evenly distributed or sine function along the horizontal line, ignoring lateral deformation of the dam, depending on debris flow three-dimensional incompressible fluid and the following formula was given: 

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18899
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
Recommended Citation
GB/T 7714
李昆. 考虑流固耦合效应的泥石流作用下拦砂坝动力响应分析[D]. 北京. 中国科学院大学,2016.
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