泥石流对桥墩的冲击作用研究

发布时间：2018-04-09 15:50

本文选题：泥石流　切入点：桥墩　出处：《西南交通大学》2014年硕士论文

【摘要】：泥石流是山区常见的自然灾害,而我国国土面积约有三分之二是山区地形,因此泥石流在我国,特别是西部地区分布相当广泛,灾害比较严重。随着我国山区经济的发展和环境污染的加剧；公路、铁路中的桥涵等工程设施遭受泥石流灾害的概率亦随之增加。桥梁作为道路的关键部位,一旦被泥石流冲毁,就会造成长时间的交通中断和巨大经济损失。因此,为了减小桥梁结构在泥石流冲击作用下的损坏,保障人们的生命安全,分析桥墩在泥石流冲击作用下的响应有着重要的理论意义和实用价值。本文首先简要介绍了泥石流的基本特性,研究了影响泥石流冲击作用的重要参数,对泥石流模拟的物理模型、数学模型和湍流模型等三种计算模型进行深入分析。在此基础上,一方面采用ANSYS瞬态分析模拟了泥石流中的整体冲击力和和大石块冲击力对桥墩的影响,另一方面采用ANSYS Workbench模拟了泥石流与桥墩的流固耦合,最终得到如下结论： (1)泥石流整体冲击力是桥墩的产生位移的主要因素,同时桥墩位移会因大石块的冲击进一步增加,增加量可达60%多。 (2)桥墩的应力、位移主要受到泥石流的容重、速度以及桥墩自身刚度的影响。当同一桥墩在泥石流冲击作用下时,其最大位移会随着泥石流流速的增加、容重的增大而相应增大。 (3)当桥墩受到冲击时,桥墩承受冲剪形式的荷载,墩底会出现较大的拉应力,如果此时墩底配筋不足,混凝土可能会开裂,甚至破坏；同时,桥墩受到大石块冲击的位置会出现明显的应力集中。 (4)通过计算流体动力学软件对泥石流对桥墩的冲击作用进行了数值模拟,得到了泥石流的体积分布情况、速度流线图和桥墩所受压力图,对泥石流冲击作用下桥墩的防护有着理论意义和工程参考价值。 (5)将泥石流体考虑为均质体计算出冲击力的结果,与《泥石流灾害防治工程设计规范》中的计算公式计算的结果相比,约偏小30%。 (6)相同横截面积的圆端形和矩形桥墩,在相同条件的泥石流冲击作用下,在相同条件的泥石流的冲击作用下,矩形桥墩所受冲击力远大于圆端形,约为其1.5倍,并且在墩底拐角处出现了明显的应力集中,应力和位移也远大于圆端形桥墩,桥墩可能会出现局部破坏,因此,在泥石流灾害易发区,如果架设桥墩宜采用圆端形桥墩。
[Abstract]:Debris flow is a common natural disaster in mountainous area, and the land area of our country is about 2/3. Therefore, debris flow is widely distributed in our country, especially in the western region, and the disaster is quite serious.With the development of mountain economy and the aggravation of environmental pollution, the probability of debris flow disaster in highway, railway bridge and culvert is increasing.As the key part of the road, once destroyed by debris flow, the bridge will cause a long period of traffic disruption and huge economic losses.Therefore, in order to reduce the damage of bridge structure under the impact of debris flow, and to ensure the safety of people's lives, it is of great theoretical significance and practical value to analyze the response of bridge pier under the impact of debris flow.In this paper, the basic characteristics of debris flow are briefly introduced, and the important parameters that affect the impact of debris flow are studied. The physical model, mathematical model and turbulence model of debris flow simulation are deeply analyzed.On the basis of this, on the one hand, ANSYS transient analysis is used to simulate the influence of the whole impact force and the large rock impact force on the pier, on the other hand, the fluid-structure coupling between the debris flow and the pier is simulated by ANSYS Workbench, and the conclusion is as follows:1) the whole impact force of debris flow is the main factor of the displacement of the bridge pier, and the displacement of the pier will be further increased by the impact of large rocks, and the increase can reach more than 60%.2) the stress and displacement of the pier are mainly affected by the bulk density, velocity and stiffness of the pier.When the same pier is under the impact of debris flow, the maximum displacement will increase with the increase of debris flow velocity and bulk density.3) when the pier is impacted, the pier will bear the load in the form of scour and shear, and the tensile stress will appear at the bottom of the pier. If there is insufficient reinforcement at the bottom of the pier at this time, the concrete may crack or even destroy; at the same time,There will be obvious stress concentration in the position where the pier is impacted by large rocks.4) the impact of debris flow on bridge piers is simulated numerically by computational fluid dynamics software, and the volume distribution of debris flow, the velocity streamline diagram and the pressure diagram of bridge pier are obtained.It has theoretical significance and engineering reference value for the protection of bridge piers under the impact of debris flow.5) considering the debris flow body as homogeneous body, the result of calculating the impact force is about 30% smaller than that of the calculation formula in "Design Code for debris flow disaster Prevention Engineering".The circular end and rectangular piers with the same cross-sectional area, under the same conditions of debris flow impact and under the same conditions of debris flow impact, the impact force of rectangular pier is much larger than that of circular end shape, about 1.5 times.And there is obvious stress concentration at the corner of pier bottom, and the stress and displacement are much larger than the round end pier, and the pier may be destroyed locally. Therefore, in the debris flow disaster prone area, the circular end pier should be used if the pier is erected.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P642.23;U442.2

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