基于有限元的淤地坝渗透分析

发布时间：2018-07-17 01:09

【摘要】：淤地坝是黄土高原重要的水土保持工程措施。随着淤地坝库容内淤积的泥沙逐年增加,在拦蓄等量洪水时,水位就会随着淤积的增加而增加,进而使淤地坝内渗流浸润线抬升,渗透坡降增大。当渗透坡降大于淤地坝筑坝土料的临界渗透坡降时,就会发生渗透形变,进而导致淤地坝的渗透破坏,渗透破坏是黄土高原淤地坝常见的破坏形式之一。开展淤地坝渗透分析研究,对于探索和解释淤地坝内渗流场分布、渗流场影响因素,防止淤地坝渗透破坏,进行水土保持和指导淤地坝工程设计具有重要意义和实用价值。本文采用公式法、有限元法和ANSYS CFX软件,研究了不同方法、不同淤积年限和狭窄沟道地形对淤地坝内渗流浸润线、渗透坡降和渗流出逸点的影响等问题,并得出了以下结论:1、基于ANSYS Workbench平台的CFX流体数值仿真分析技术效果最佳。分析对比公式法、理正有限元法、ANSYS CFX法:公式法在分析过程中,最为传统,也是目前认知力度最好的方法,但是该方法采用的是传统的解方程的方法,难以应对各向异性土层,对多种类型土层兼容性较差。理正有限元法方法新颖,操作简便,但是仍然没有三维分析功能,更没有全地形淤地坝渗流场建模能力。只有ANSYS CFX中存在全地形淤地坝渗流场分析能力,且对应的精度较高。2、在洪水总量不变的情况下,随着淤地坝内的淤积量增加,淤地坝渗流出逸点,渗透坡降都会增大,且增大的幅度较大。这对于淤地坝的渗透稳定有不利影响,因此在对淤地坝进行设计时,必须进行相应的计算与校核,在必要的情况下,设计相应的排水措施和反滤体,以降低坝体内的浸润线。3、沟道形状对淤地坝有一定的影响(本例中为17.78%)。这种影响主要表现为3个方面,(1)抬升作用,沟道两侧的岸坡提升了底部高程,从而使淤地坝内渗流场高度提升;(2)阻挡作用,沟道两侧岸坡如果存在凹陷,在水位低的时候作用相当于水池,可以阻挡水流通过,在水位高的时候作用相当于宽顶堰,降低浸润线高度;(3)汇聚作用,使水流沿岸坡下降的方向,向沟道中心线方向汇聚,增大中心线方向上的渗流出逸点高程。
[Abstract]:Silt dam is an important engineering measure of soil and water conservation in the Loess Plateau. With the increase of silt in silt dam, the water level will increase with the increase of siltation, and then the seepage line will rise and the seepage slope will increase. When the seepage slope is larger than the critical seepage slope of soil material for dam construction, seepage deformation will occur, which will lead to seepage failure of silt dam, which is one of the common failure forms of silt dam in the Loess Plateau. The research on seepage analysis of silt dam is of great significance and practical value in exploring and explaining the distribution of seepage field in silt dam, influencing factors of seepage field, preventing seepage damage of silt dam, carrying out soil and water conservation and guiding silt dam engineering design. By using formula method, finite element method and ANSYS CFX software, the influence of different methods, different siltation years and narrow channel topography on seepage line, seepage gradient and seepage escape point in silt dam are studied. The following conclusions are drawn as follows: 1. The CFX fluid numerical simulation based on ANSYS Workbench is the best. In the process of analysis, the formula method is the most traditional and the best method of cognition at present, but the traditional method of solving equations is adopted in this method, so it is difficult to deal with anisotropic soil layer. Poor compatibility for many types of soil layers. The straightening finite element method is novel and easy to operate, but it still does not have the function of three-dimensional analysis and the ability of modeling the seepage field of a full-terrain silt dam. Only ANSYS CFX has the ability to analyze the seepage field of the whole terrain silt dam, and the corresponding accuracy is higher. When the total flood amount is constant, the seepage escape point of the silt dam will increase, and the seepage slope will increase with the increase of the siltation quantity in the silt dam. And the amplitude of the increase is larger. This has an adverse effect on the seepage stability of silt dams. Therefore, when designing silt dams, they must be calculated and checked accordingly, and, if necessary, the corresponding drainage measures and filters should be designed. In order to reduce the infiltration line. 3 in the dam body, the channel shape has certain influence on the silt dam (in this case, 17.78%). This effect is mainly manifested in three aspects: (1) uplifting, raising the bottom elevation of the bank slope on both sides of the channel, thus elevating the height of seepage field in the silt dam; (2) blocking effect, if there is a depression on the bank slope on both sides of the channel, When the water level is low, it acts as a pool, which can block the passage of water, and when the water level is high, it acts as a wide top Weir and reduces the height of the infiltrating line; (3) the converging effect causes the direction of the slope along the river to fall, and converges to the direction of the central line of the channel. Increase the height of the escape point in the direction of the center line.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157.31

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