土石坝坝下涵管三维渗流有限元分析

发布时间：2018-11-23 18:10

【摘要】：土石坝建造在水利工程中有着悠久的历史,和其他坝型相比较,土石坝造价低,因而被作为一种普遍使用的坝体类型。其中埋设于土石坝的坝下涵管是一种重要的输水建筑物,坝下涵管直接埋设于坝体,需要承受顶部坝体填土压力、地基不均匀沉降的影响,在与坝体填土接触部位还需要承受渗流冲刷的作用,破坏后会对工程造成严重的损失。一直以来,在土石坝的规划设计及参数分析中,通常偏重于渗流分析和稳定计算;对涵管的研究则偏重于涵管的受力、沉降的计算等结构计算分析。而对于在坝体稳定渗流期,涵管与坝体填土接触渗流的研究开展较少。本文为了研究坝下涵管周围接触渗流问题,介绍了渗流理论的发展历程和基本方法,建立了稳定渗流期坝体及坝下涵管三维有限元分析模型。通过对土石坝常见非线性问题分析模型的比较,最终确定摩尔-库伦模型作为本文土石坝有限元分析的本构模型。针对不同计算工况,分别建立了坝体及坝下涵管应力计算模型、坝体及坝下涵管三维渗流分析计算模型。根据所开展的工作得出了以下结论:(1)涵管所受应力及竖向位移计算上埋式涵管管顶垂直土压力时,应考虑涵管两侧土体的不均匀沉降的“拖曳摩擦”作用所带来的应力增加。涵管顶部所受竖向应力呈不均匀分布,在涵管上方,随着距离涵管顶部中心线的距离的增加,涵管顶部所受到的竖向应力增加。在涵管外侧,竖向应力先减小后增加,逐渐趋于稳定。随着距离涵管中心线距离的增加,涵管顶部竖向位移逐渐增加,之后逐渐趋于稳定。(2)无截水环时涵管周围渗流涵管周围土体渗流速度、渗流量随涵管周围土体渗透系数的升高而增大,当不设置截水环时,即使涵管周围土体的渗透系数有所变化,但沿程渗透坡降几乎无变化,而仅在渗流出口处,渗透坡降随着涵管周围土体渗透系数的增大而略有减小。(3)截水环对涵管周围渗流场的影响涵管增设截水环可以有效降低涵管周围渗流速度、渗流量,降低涵管周围渗流出口处的渗透坡降,对预防涵管周围土体接触冲刷的发生起到重要作用。截水环的效果也跟截水环的尺寸和数量有关,在一定的尺寸和数量范围情况下,截水环的数量越多、尺寸越大,其防止涵管周围渗透破坏的效果也越好。超过一定的尺寸和数量后,截水环的影响效果差别不大。
[Abstract]:Earth-rock dam construction has a long history in water conservancy engineering. Compared with other dam types, earth-rock dam has a low cost, so it is widely used as a dam body type. The culvert under the dam buried in the earth-rock dam is an important water conveyance structure, and the culvert under the dam is directly buried in the dam body, which needs to bear the influence of the fill earth pressure on the top dam and the uneven settlement of the foundation. In contact with the fill of the dam, it is necessary to bear the role of seepage and scour, which will cause serious damage to the project. In the planning, design and parameter analysis of earth-rock dams, emphasis is usually placed on seepage analysis and stability calculation, while the study on culverts is focused on structural calculation and analysis such as the stress of culvert and the calculation of settlement. However, the research on contact seepage between culvert and fill is less in the steady seepage period. In this paper, in order to study the contact seepage around culvert under dam, the development history and basic method of seepage theory are introduced, and the three-dimensional finite element analysis model of dam body and culvert under dam during steady seepage period is established. Through the comparison of common nonlinear analysis models of earth-rock dams, the Moor-Coulomb model is finally determined as the constitutive model of the finite element analysis of earth-rock dams in this paper. According to different calculation conditions, the stress calculation models of dam body and culvert under dam, and the three-dimensional seepage analysis model of dam body and culvert under dam are established respectively. According to the work carried out, the following conclusions are obtained: (1) when the stress and vertical displacement of the culvert pipe are calculated, the vertical earth pressure of the top of the buried culvert pipe is calculated. The stress increase caused by "drag friction" of uneven settlement of soil on both sides of culvert should be considered. The vertical stress on the top of culvert is distributed unevenly, and the vertical stress on the top of culvert increases with the increase of distance from the centerline of culvert top. On the outside of the culvert, the vertical stress decreases first and then increases, and then tends to be stable. With the increase of the distance from the center line of culvert, the vertical displacement of culvert top increases gradually, and then tends to stabilize gradually. (2) seepage velocity of soil around culvert pipe without water cut ring, The seepage flow rate increases with the increase of soil permeability coefficient around culvert pipe. Even if the permeability coefficient of soil around culvert pipe is changed, the seepage gradient is almost unchanged, but only at the seepage outlet. The seepage gradient decreases slightly with the increase of soil permeability coefficient around culvert pipe. (3) the influence of water cut ring on seepage field around culvert pipe can effectively reduce the seepage velocity and flow rate around culvert pipe. Reducing the seepage slope at the seepage outlet around culvert plays an important role in preventing contact erosion of soil around culvert. The effect of the water cutoff ring is also related to the size and quantity of the intercepting ring. Under certain size and quantity range, the larger the number and the larger the size, the better the effect of preventing seepage damage around the culvert. After a certain size and quantity, the effect of the water cutoff ring is not different.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TV223.4

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