本文選題：黃土地區(qū) + 泥石流沖擊�。� 參考：《蘭州交通大學(xué)》2017年碩士論文

【摘要】：我國(guó)黃土分布范圍極廣,總覆蓋面積約為640000km2;黃土是一種特殊的土狀堆積物,抗侵蝕和抗重力剝蝕的能力低;容易發(fā)生的溝岸坍塌、滑坡、溜坍等失穩(wěn)現(xiàn)象為黃土地區(qū)泥石流的形成提供了主要的物質(zhì)來(lái)源;侵蝕溝、潛蝕、溝岸坡積黃土等現(xiàn)象也能為泥石流提供物質(zhì)來(lái)源。近年,黃土地區(qū)泥石流沖毀線(xiàn)路構(gòu)造物特別是橋梁的事件日趨增多;以此作為研究背景,并以國(guó)內(nèi)外對(duì)泥石流沖擊性能的研究方法和結(jié)論為基礎(chǔ);同時(shí)結(jié)合流體力學(xué)的經(jīng)驗(yàn)、成果,對(duì)黃土地區(qū)泥石流的成分和主要性質(zhì)進(jìn)行了綜合分析研究;利用分析的結(jié)果,借助于軟件ANSYS Workbench建立了共15種泥石流沖擊橋墩的模擬工況,以針對(duì)陣發(fā)性、持續(xù)性?xún)煞N泥石流活動(dòng)對(duì)橋墩沖擊過(guò)程中的眾多問(wèn)題進(jìn)行雙向流固耦合模擬。經(jīng)過(guò)對(duì)模擬結(jié)果的綜合分析得出以下結(jié)論:(1)堰塞湖崩塌后形成的陣發(fā)性泥石流對(duì)下游橋墩的危害是災(zāi)難性的,以初始泥石流液面高度為16 m例,橋墩混凝土在抗拉、抗剪方面都不能滿(mǎn)足要求,應(yīng)力完全由對(duì)應(yīng)的鋼筋承擔(dān)。另外,受壓區(qū)混凝土也處于危險(xiǎn)的邊緣。因此,在此類(lèi)工況下即使適筋橋墩仍有被摧毀的危險(xiǎn)。(2)模擬結(jié)果與“泥石流災(zāi)害防治工程設(shè)計(jì)規(guī)范”中推薦的泥石流沖擊力計(jì)算公式計(jì)算結(jié)果對(duì)比發(fā)現(xiàn)規(guī)范推薦公式安全。(3)大石塊的沖擊主要從三個(gè)方面影響橋墩安全:強(qiáng)度、穩(wěn)定性和破壞碰撞點(diǎn)混凝土引起的局部破壞。(4)由于橋墩的阻礙作用改變了泥石流高速運(yùn)動(dòng)的流場(chǎng),加強(qiáng)了局部下切,解釋了泥石流災(zāi)害中迎沖面附近沖擊坑的形成原因。(5)施做蓋梁可以增加橋墩整體的強(qiáng)度和穩(wěn)定性。(6)沖擊角度主要在兩個(gè)方面對(duì)橋墩產(chǎn)生影響:改變等效迎沖面的面積和前墩柱對(duì)后墩柱附近流場(chǎng)的影響。(7)經(jīng)過(guò)綜合數(shù)據(jù)分析,在泥石流多發(fā)區(qū)域,為更好的滿(mǎn)足橋墩強(qiáng)度和穩(wěn)定性的需要,盡量設(shè)計(jì)圓形截面橋墩。另外,針對(duì)每一問(wèn)題給出了針對(duì)性的改進(jìn)意見(jiàn)。
[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.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：U442.2;P642.23

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