多年冻土区输电塔锥柱基础承载特性研究

发布时间：2019-03-08 08:25

【摘要】：随着我国西部大开发战略的不断深入,跨越多年冻土区的输电线路建设日益增多,其面对的冻土工程问题也不可避免。对于穿越冻土地质的输电线路工程,杆塔基础决定其成败。而杆塔基础的难点又在于保证冻土基础的稳定性。冻土具有较大的冻胀作用,对建(构)筑物具有较为明显的冻胀破坏。杆塔基础在冻土中易产生较大的切向冻胀力,对基础产生冻拔作用,从而影响基础的稳定性。为此,前人设计了一种能够依靠自身的截面形式而能够全部或部分消除切向冻胀力的新型基础,即锥柱基础。本文以格尔木—拉萨±400kV直流输电线路工程为背景,依托ABAQUS有限元分析软件,建立了输电塔锥柱基础与周围的冻土土体共同作用时的有限元分析模型,对多年冻土区锥柱基础的上拔、下压承载性能展开了研究。首先,通过建立不同尺寸的锥柱基础及其改进型式的基础在冻土活动层分别处于冻结和融化状态时的有限元模型,研究了冻土地区锥柱基础在受到竖向上拔荷载时的上拔承载能力及其破坏模式,并讨论了不同基础型式、不同扩展板直径以及不同基础高度等因素对基础抗拔承载性能的影响。然后,通过建立锥柱基础的三维有限元模型,研究了在加入水平荷载以后对锥柱基础上拔性能的影响。采用逐级加载的方式,对锥柱基础在仅受竖向上拔荷载以及受到上拔荷载与水平荷载同时作用时所发生的位移进行了对比分析,并得出了在进行冻土基础的上拔稳定验算过程中,水平力与上拔力比值在0.15~0.4之间时,水平力的折减系数可建议取值为0.85~0.9。最后,建立了锥柱基础在竖向下压荷载作用时的有限元模型,研究了在冻土地区锥柱基础受到竖向下压荷载时的下压承载能力及其破坏模式,并分析讨论了不同基础底面面积和不同的基础高度对锥柱基础下压承载性能的影响规律。锥柱基础是一种专门应用在冻土地区的杆塔基础,在输电线路工程建设中的应用经验较少且理论计算相对不足。本文用数值模拟的方法对锥柱基础的上拔、下压承载特性进行了研究,为多年冻土区锥柱基础的设计计算提供了一定的理论依据,为相关的设计人员提供了一定的参考。
[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 卤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.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM75

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