本文選題：泥石流　切入點：橋墩　出處：《西南交通大學(xué)》2014年碩士論文

【摘要】：泥石流是山區(qū)常見的自然災(zāi)害,而我國國土面積約有三分之二是山區(qū)地形,因此泥石流在我國,特別是西部地區(qū)分布相當(dāng)廣泛,災(zāi)害比較嚴(yán)重。隨著我國山區(qū)經(jīng)濟的發(fā)展和環(huán)境污染的加��；公路、鐵路中的橋涵等工程設(shè)施遭受泥石流災(zāi)害的概率亦隨之增加。橋梁作為道路的關(guān)鍵部位,一旦被泥石流沖毀,就會造成長時間的交通中斷和巨大經(jīng)濟損失。因此,為了減小橋梁結(jié)構(gòu)在泥石流沖擊作用下的損壞,保障人們的生命安全,分析橋墩在泥石流沖擊作用下的響應(yīng)有著重要的理論意義和實用價值。 本文首先簡要介紹了泥石流的基本特性,研究了影響泥石流沖擊作用的重要參數(shù),對泥石流模擬的物理模型、數(shù)學(xué)模型和湍流模型等三種計算模型進(jìn)行深入分析。在此基礎(chǔ)上,一方面采用ANSYS瞬態(tài)分析模擬了泥石流中的整體沖擊力和和大石塊沖擊力對橋墩的影響,另一方面采用ANSYS Workbench模擬了泥石流與橋墩的流固耦合,最終得到如下結(jié)論： (1)泥石流整體沖擊力是橋墩的產(chǎn)生位移的主要因素,同時橋墩位移會因大石塊的沖擊進(jìn)一步增加,增加量可達(dá)60%多。 (2)橋墩的應(yīng)力、位移主要受到泥石流的容重、速度以及橋墩自身剛度的影響。當(dāng)同一橋墩在泥石流沖擊作用下時,其最大位移會隨著泥石流流速的增加、容重的增大而相應(yīng)增大。 (3)當(dāng)橋墩受到?jīng)_擊時,橋墩承受沖剪形式的荷載,墩底會出現(xiàn)較大的拉應(yīng)力,如果此時墩底配筋不足,混凝土可能會開裂,甚至破壞；同時,橋墩受到大石塊沖擊的位置會出現(xiàn)明顯的應(yīng)力集中。 (4)通過計算流體動力學(xué)軟件對泥石流對橋墩的沖擊作用進(jìn)行了數(shù)值模擬,得到了泥石流的體積分布情況、速度流線圖和橋墩所受壓力圖,對泥石流沖擊作用下橋墩的防護有著理論意義和工程參考價值。 (5)將泥石流體考慮為均質(zhì)體計算出沖擊力的結(jié)果,與《泥石流災(zāi)害防治工程設(shè)計規(guī)范》中的計算公式計算的結(jié)果相比,約偏小30%。 (6)相同橫截面積的圓端形和矩形橋墩,在相同條件的泥石流沖擊作用下,在相同條件的泥石流的沖擊作用下,矩形橋墩所受沖擊力遠(yuǎn)大于圓端形,約為其1.5倍,并且在墩底拐角處出現(xiàn)了明顯的應(yīng)力集中,應(yīng)力和位移也遠(yuǎn)大于圓端形橋墩,橋墩可能會出現(xiàn)局部破壞,因此,在泥石流災(zāi)害易發(fā)區(qū),如果架設(shè)橋墩宜采用圓端形橋墩。
[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.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P642.23;U442.2

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