【摘要】：隨著我國西部大開發(fā)戰(zhàn)略的不斷深入,跨越多年凍土區(qū)的輸電線路建設(shè)日益增多,其面對的凍土工程問題也不可避免。對于穿越凍土地質(zhì)的輸電線路工程,桿塔基礎(chǔ)決定其成敗。而桿塔基礎(chǔ)的難點又在于保證凍土基礎(chǔ)的穩(wěn)定性。凍土具有較大的凍脹作用,對建(構(gòu))筑物具有較為明顯的凍脹破壞。桿塔基礎(chǔ)在凍土中易產(chǎn)生較大的切向凍脹力,對基礎(chǔ)產(chǎn)生凍拔作用,從而影響基礎(chǔ)的穩(wěn)定性。為此,前人設(shè)計了一種能夠依靠自身的截面形式而能夠全部或部分消除切向凍脹力的新型基礎(chǔ),即錐柱基礎(chǔ)。本文以格爾木—拉薩±400kV直流輸電線路工程為背景,依托ABAQUS有限元分析軟件,建立了輸電塔錐柱基礎(chǔ)與周圍的凍土土體共同作用時的有限元分析模型,對多年凍土區(qū)錐柱基礎(chǔ)的上拔、下壓承載性能展開了研究。首先,通過建立不同尺寸的錐柱基礎(chǔ)及其改進型式的基礎(chǔ)在凍土活動層分別處于凍結(jié)和融化狀態(tài)時的有限元模型,研究了凍土地區(qū)錐柱基礎(chǔ)在受到豎向上拔荷載時的上拔承載能力及其破壞模式,并討論了不同基礎(chǔ)型式、不同擴展板直徑以及不同基礎(chǔ)高度等因素對基礎(chǔ)抗拔承載性能的影響。然后,通過建立錐柱基礎(chǔ)的三維有限元模型,研究了在加入水平荷載以后對錐柱基礎(chǔ)上拔性能的影響。采用逐級加載的方式,對錐柱基礎(chǔ)在僅受豎向上拔荷載以及受到上拔荷載與水平荷載同時作用時所發(fā)生的位移進行了對比分析,并得出了在進行凍土基礎(chǔ)的上拔穩(wěn)定驗算過程中,水平力與上拔力比值在0.15~0.4之間時,水平力的折減系數(shù)可建議取值為0.85~0.9。最后,建立了錐柱基礎(chǔ)在豎向下壓荷載作用時的有限元模型,研究了在凍土地區(qū)錐柱基礎(chǔ)受到豎向下壓荷載時的下壓承載能力及其破壞模式,并分析討論了不同基礎(chǔ)底面面積和不同的基礎(chǔ)高度對錐柱基礎(chǔ)下壓承載性能的影響規(guī)律。錐柱基礎(chǔ)是一種專門應(yīng)用在凍土地區(qū)的桿塔基礎(chǔ),在輸電線路工程建設(shè)中的應(yīng)用經(jīng)驗較少且理論計算相對不足。本文用數(shù)值模擬的方法對錐柱基礎(chǔ)的上拔、下壓承載特性進行了研究,為多年凍土區(qū)錐柱基礎(chǔ)的設(shè)計計算提供了一定的理論依據(jù),為相關(guān)的設(shè)計人員提供了一定的參考。
[Abstract]:With the deepening of the western development strategy of our country, the construction of transmission lines across permafrost areas is increasing day by day, and the permafrost engineering problems faced by them are inevitable. For transmission line engineering through frozen soil geology, tower foundation determines its success or failure. And the difficulty of tower foundation is to ensure the stability of frozen soil foundation. Frozen soil has great frost heave effect and obvious frost heave damage to buildings. The tower foundation is easy to produce large tangential frost heaving force in frozen soil, and freeze-pull effect on the foundation, thus affecting the stability of the foundation. For this reason, the predecessors designed a new type of foundation which can completely or partially eliminate tangential frost heave force by its own cross-section form, I. E., cone column foundation. Under the background of Golmud-Lhasa 鹵400kV HVDC transmission line project and relying on ABAQUS finite element analysis software, a finite element analysis model for the interaction between cone column foundation of transmission tower and surrounding frozen soil is established in this paper. The bearing capacity of cone column foundation in permafrost region is studied. Firstly, the finite element models of cone column foundations with different sizes and their modified types are established when the frozen and thawed layers are frozen and melted, respectively. In this paper, the uplift bearing capacity and failure mode of cone column foundation under vertical pull-up load in frozen soil area are studied, and the effects of different types of foundation, different diameter of expanded plate and different height of foundation on the bearing capacity of foundation under vertical pull-up load are discussed. Then, a three-dimensional finite element model of cone column foundation is established, and the influence of horizontal load on the pull-out performance of cone column foundation is studied. In this paper, the displacement of cone column foundation subjected to vertical pull-out load and simultaneous action of uplift load and horizontal load is analyzed by means of step-by-step loading method, and the displacement of cone column foundation under vertical pull-out load and horizontal load is analyzed. In the process of checking the uplift stability of frozen soil foundation, when the ratio of horizontal force to pull-up force is between 0.15 and 0.4, the reduction factor of horizontal force can be recommended to be 0.85 脳 0.9. Finally, the finite element model of cone column foundation under vertical downward pressure is established, and the load carrying capacity and failure mode of cone column foundation under vertical downward compression load in frozen soil area are studied. The influence of different base area and height on the compressive behavior of cone column foundation is analyzed and discussed in this paper, and the influence of the base area and height on the compressive bearing capacity of cone column foundation is analyzed and discussed. Cone-column foundation is a kind of tower-pole foundation which is specially used in permafrost area. The application experience of cone-column foundation in transmission line construction is less and the theoretical calculation is relatively insufficient. In this paper, the bearing capacity of cone column foundation is studied by numerical simulation method, which provides a certain theoretical basis for the design and calculation of cone column foundation in frozen soil area for many years, and provides a certain reference for relevant designers.
【學(xué)位授予單位】：東北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM75

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