本文選題：多年凍土區(qū) + 橋臺(tái)　； 參考：《蘭州交通大學(xué)》2017年碩士論文

【摘要】：在多年凍土區(qū)鐵路的建設(shè)和運(yùn)營過程中,部分橋梁結(jié)構(gòu)出現(xiàn)了一些病害,比如橋臺(tái)受臺(tái)后路基填土凍脹力的作用產(chǎn)生了傾斜變形,最終使得梁端與橋臺(tái)之間的縫隙擠死。對(duì)于多年凍土地區(qū)橋墩、臺(tái)變形的研究,我國主要集中在多年凍土區(qū)工程病害調(diào)查和治理,其重點(diǎn)在于橋墩、臺(tái)基礎(chǔ)的融沉和凍拔變形,橋臺(tái)的水平凍脹力及變形問題少有研究。2013年底中鐵西北研究院在某鐵路的調(diào)查中發(fā)現(xiàn),某橋西寧端的橋臺(tái)發(fā)生了明顯的前傾變形,后經(jīng)開挖發(fā)現(xiàn),橋臺(tái)的樁基被剪斷。這表明了多年凍土區(qū)橋臺(tái)臺(tái)后水平凍脹力對(duì)橋臺(tái)危害是存在的,需研究進(jìn)行治理。本文根據(jù)現(xiàn)有的文獻(xiàn)資料對(duì)多年凍土區(qū)橋臺(tái)臺(tái)后水平凍脹力的形成機(jī)理、影響因素和橋涵病害及其原因進(jìn)行分析總結(jié);對(duì)某典型病害橋梁基礎(chǔ)及過渡段路堤病害原因及現(xiàn)狀進(jìn)行分析;并以該橋?yàn)榉治鰧?duì)象,借助有限元軟件ANSYS,建立有限元模型,模擬橋臺(tái)及周圍土體凍結(jié)過程的溫度場,得出橋臺(tái)附近的地溫場變化特征,并與距橋臺(tái)較遠(yuǎn)處土體(不受橋臺(tái)影響的路基及以下土體)進(jìn)行了對(duì)比分析,得出了橋臺(tái)對(duì)附近的地溫場影響較大,增大了土體的換熱速度,使周圍土體溫度場進(jìn)行了重分布,加快了凍融循環(huán);將該溫度場與結(jié)構(gòu)模型進(jìn)行熱-力耦合分析,研究了橋臺(tái)臺(tái)后水平凍脹力的大小和發(fā)展分布以及橋臺(tái)受到凍脹力的變形位移情況。通過數(shù)值模擬橋臺(tái)周圍的地溫場,分析表明距橋臺(tái)較近的土體其溫度變化較快,距橋臺(tái)較遠(yuǎn)處受橋臺(tái)換熱邊界條件影響很小。與天然地基自上而下的單向凍結(jié)過程相比,橋臺(tái)修建后,橋臺(tái)附近土體熱量發(fā)生了變遷,原有的地溫?zé)崞胶獗淮蚱?熱平衡條件的改變促使土體的溫度狀態(tài)發(fā)生變化,這些變化對(duì)橋臺(tái)穩(wěn)定性具有不利影響。橋臺(tái)在臺(tái)后水平凍脹力作用下向前移動(dòng),在臺(tái)底法向凍脹力和臺(tái)后水平力共同作用下發(fā)生前傾。各個(gè)月份的位移值不相同,橋臺(tái)臺(tái)后人為上限以上土體隨著時(shí)間的變化發(fā)生著凍融循環(huán)。隨著冷暖季的交替,橋臺(tái)和梁體間預(yù)留的縫隙不斷變小最后擠壓在一起,這與實(shí)際觀測到的現(xiàn)象一致,證明本模型是可靠的。
[Abstract]:In the process of railway construction and operation in permafrost region, some bridge structures appear some diseases, for example, the frost heaving force of embankment after abutment causes slope deformation, and finally causes the gap between beam end and abutment to die. For the study of bridge pier and abutment deformation in permafrost region, our country mainly focuses on the investigation and treatment of engineering diseases in permafrost region, with emphasis on the thawing and freeze-drawing deformation of pier and abutment foundation. The horizontal frost heaving force and deformation of abutment are seldom studied. In the investigation of a railway at the end of 2013, the Northwest Research Institute of China Railway found that the abutment at Xining end of the bridge had obvious forward deformation, and after excavation, the pile foundation of abutment was cut off. This indicates that the horizontal frost heaving force behind abutment in permafrost region is harmful to abutment. In this paper, the formation mechanism of horizontal frost heaving force behind abutment in permafrost region, influencing factors, bridge culvert diseases and their causes are analyzed and summarized according to the existing literature. This paper analyzes the causes and present situation of the foundation and embankment damage of a typical diseased bridge, and takes the bridge as an analysis object, establishes a finite element model with the help of the finite element software ANSYS, and simulates the temperature field of the freezing process of the abutment and the surrounding soil. The variation characteristics of ground temperature field near abutment are obtained, and compared with soil mass (subgrade and soil below) which is not affected by abutment, it is concluded that the influence of abutment on ground temperature field is great and the heat transfer rate of soil is increased. The temperature field of surrounding soil is redistributed to accelerate the freeze-thaw cycle, and the thermal-mechanical coupling analysis between the temperature field and the structure model is carried out. The magnitude and development distribution of horizontal frost heaving force behind abutment and the deformation and displacement of abutment subjected to frost heave force are studied. Through the numerical simulation of the ground temperature field around abutment, the analysis shows that the temperature of soil near abutment changes rapidly, and the influence of abutment heat transfer boundary condition is very small in the distance from abutment. Compared with the unidirectional freezing process of natural foundation from top to bottom, after the bridge abutment is built, the heat of soil around the abutment has changed, the original ground temperature and heat balance has been broken, and the change of thermal equilibrium condition has promoted the change of soil temperature state. These changes have adverse effects on abutment stability. The abutment moves forward under the action of horizontal frost heaving force behind the abutment and tilts forward under the combined action of normal frost heaving force at the bottom of the platform and horizontal force behind the abutment. The displacement values vary from month to month, and the soil above the upper limit of abutment has a freeze-thaw cycle over time. With the alternation of cold and warm seasons the gap between abutment and beam becomes smaller and finally squeezed together which is consistent with the observed phenomenon and proves that the model is reliable.
【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
【分類號(hào)】：U442.2

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