黄土地区泥石流对桥墩冲击的数值模拟研究

发布时间：2018-05-14 00:21

本文选题：黄土地区 + 泥石流冲击　；参考：《兰州交通大学》2017年硕士论文

【摘要】：我国黄土分布范围极广,总覆盖面积约为640000km2;黄土是一种特殊的土状堆积物,抗侵蚀和抗重力剥蚀的能力低;容易发生的沟岸坍塌、滑坡、溜坍等失稳现象为黄土地区泥石流的形成提供了主要的物质来源;侵蚀沟、潜蚀、沟岸坡积黄土等现象也能为泥石流提供物质来源。近年,黄土地区泥石流冲毁线路构造物特别是桥梁的事件日趋增多;以此作为研究背景,并以国内外对泥石流冲击性能的研究方法和结论为基础;同时结合流体力学的经验、成果,对黄土地区泥石流的成分和主要性质进行了综合分析研究;利用分析的结果,借助于软件ANSYS Workbench建立了共15种泥石流冲击桥墩的模拟工况,以针对阵发性、持续性两种泥石流活动对桥墩冲击过程中的众多问题进行双向流固耦合模拟。经过对模拟结果的综合分析得出以下结论:(1)堰塞湖崩塌后形成的阵发性泥石流对下游桥墩的危害是灾难性的,以初始泥石流液面高度为16 m例,桥墩混凝土在抗拉、抗剪方面都不能满足要求,应力完全由对应的钢筋承担。另外,受压区混凝土也处于危险的边缘。因此,在此类工况下即使适筋桥墩仍有被摧毁的危险。(2)模拟结果与“泥石流灾害防治工程设计规范”中推荐的泥石流冲击力计算公式计算结果对比发现规范推荐公式安全。(3)大石块的冲击主要从三个方面影响桥墩安全:强度、稳定性和破坏碰撞点混凝土引起的局部破坏。(4)由于桥墩的阻碍作用改变了泥石流高速运动的流场,加强了局部下切,解释了泥石流灾害中迎冲面附近冲击坑的形成原因。(5)施做盖梁可以增加桥墩整体的强度和稳定性。(6)冲击角度主要在两个方面对桥墩产生影响:改变等效迎冲面的面积和前墩柱对后墩柱附近流场的影响。(7)经过综合数据分析,在泥石流多发区域,为更好的满足桥墩强度和稳定性的需要,尽量设计圆形截面桥墩。另外,针对每一问题给出了针对性的改进意见。
[Abstract]:Loess in China has a very wide distribution, with a total coverage area of about 640000km2. Loess is a special soil-like deposit with low ability to resist erosion and gravity denudation. The gully bank collapses and landslides occur easily. The instability phenomena such as collapse provide the main material source for the formation of debris flow in loess area, and the phenomena such as erosion ditch, latent erosion, gully slope accumulation of loess can also provide material source for debris flow. In recent years, the events of debris flow destruction line structures, especially bridges, have been increasing in loess area, which is used as the research background, and based on the research methods and conclusions of debris flow impact performance at home and abroad, at the same time, combined with the experience of hydrodynamics, The results show that the composition and main properties of debris flow in loess area are analyzed synthetically, and 15 kinds of debris flow impact on bridge piers are established with the help of software ANSYS Workbench. Two kinds of continuous debris flow are used to simulate many problems in the impact process of bridge piers. Through the comprehensive analysis of the simulation results, the following conclusions are drawn: (1) the paroxysmal debris flow caused by the collapse of the barrier lake is disastrous to the downstream pier. In the case of the initial debris flow liquid surface height of 16 m, the concrete of the pier is in tensile resistance. Shear resistance can not meet the requirements, the stress is completely borne by the corresponding reinforcement. In addition, the compressive zone of concrete is also on the edge of danger. Therefore, The simulation results are compared with the results of the calculation formula of debris flow impact force recommended in "Design Code for debris flow disaster Prevention Engineering". The impact of large stones mainly affects the safety of bridge piers in three aspects: strength, Stability and local failure caused by concrete at impact point. 4) because of the blocking effect of bridge piers, the flow field of debris flow in high speed motion is changed, and the local downcut is strengthened. This paper explains the cause of formation of impact pits near the face of debris flow disaster. (5) the construction of cover beam can increase the strength and stability of the pier as a whole. The impact angle mainly affects the pier in two aspects: changing the equivalent face of the bridge. Area and the influence of the front pier column on the flow field near the rear pier column. In order to meet the needs of strength and stability of bridge pier, circular section pier is designed as far as possible in debris flow area. In addition, aiming at each problem, the paper gives some suggestions to improve it.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U442.2;P642.23

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