双层堤基渗透破坏发展机理研究

发布时间：2019-01-03 18:38

【摘要】：双层堤基广泛存在于江河中下游地区，渗透破坏是该类堤基中出险率最高的破坏形式，多年来针对堤后渗透破坏产生条件的研究已经取得了一定的成果，但是对于渗流出口（工程中也称管涌口）形成后，集中渗流通道（工程中也称管涌通道）的断面扩展和上溯仍然缺乏深刻的认识，而该通道的发展直接关系到渗流出口形成后渗透破坏危险性的大小，因而本文针对双层堤基中管涌口产生以后，在强弱透水层之间产生的管涌通道进行研究，其发展包含通道断面扩展和尖端上溯两个方面，本文主要针对这两个方面开展工作，具体内容为： 1.管涌通道发展的机理性研究，包含通道扩展和上溯两个部分。在通道扩展方面，以通道边壁砂颗粒作为研究对象，通过颗粒的稳定状态来判定通道扩展的最终形态，砂颗粒的稳定性由其受力状态所决定，在颗粒受力平衡的分析中，引用河流动力学中的相关概念与公式，考虑了不同粒径砂颗粒之间的相互作用和起动标准，通过计算得到了作用在砂颗粒上的临界起动速度，考虑通道内流速的紊动、非均匀分布和通道内的水流特性，采用通道断面平均流速来作为通道扩展的判定标准，该标准具有方便测量和简单易用等特点；在通道上溯方面，提出了以尖端坡降作为通道是否上溯的评判标准，通道上溯后，尖端坡降由于通道各处断面形状的变化，其变化趋势分为稳定和增长两种，如果尖端坡降稳定，则通道能够保持稳定，如果尖端坡降增加，则通道无法稳定会持续上溯，直至贯穿堤基。 2.管涌通道发展的试验研究，包含通道扩展和上溯两个部分。在通道扩展方面，采用两种模型尺寸进行了多组试验，试验结果显示在远端和通道内水头差较小时，渗透力对通道的扩展作用较明显，但是当水头差增大时，渗透力对通道扩展的作用减弱，此时通道内水流冲刷对通道扩展的影响则较为明显；在通道上溯方面，采用两种覆盖层模拟方法研究了通道上溯时平面和剖面的发展形态，试验结果证实了机理分析中尖端坡降的相关内容。 3.管涌通道发展的数值模拟计算，包含通道扩展和上溯两个部分。在通道扩展方面，以二维有限元渗流程序为基础，以通道断面平均流速、自然休止角和形状附加条件三条标准为断面的扩展的判定条件，以远端、通道内水头差和通道内水流流量为边界条件，模拟了通道的扩展过程，给出了通道的稳定状态；在通道上溯方面，采用多层透水地层准三维有限元程序进行通道发展的计算，兼顾计算量和计算精度，提出了一种等效代换方法，在研究通道各处断面扩展判定时采用通道实际断面形式，在三维渗流场计算时采用等效矩形断面形式，等效前后，通道内水流和通道外渗流均保持一致，计算结果给出了渗流场以及通道尖端坡降，，可用于判定通道上溯的稳定性。 4.通过程序计算结果与试验结果进行对比，验证了机理分析与程序编制的正确性，基于程序分析，对典型双层堤基管涌通道的发展进行了相关探讨。
[Abstract]:The double-layer bank is widely present in the middle and lower reaches of the river, and the seepage and destruction are the most dangerous forms in the bank. The research on the condition of the seepage and destruction of the levee for many years has achieved some results, but after the formation of the seepage outlet (also known as the pipe kick), The cross-section extension and the back-up of the concentrated seepage channel (also known as the pipe surge channel) still lack a deep understanding, and the development of the channel is directly related to the size of the risk of seepage and destruction after the formation of the seepage outlet. The development of the pipe-surge channel between the strong and weak water-permeable layer includes the extension of the channel section and the back-up of the tip. The paper mainly focuses on the two aspects, and the specific content is as follows: 1. The machine rational research of the development of the piping channel Research, including channel extension and back-up In the aspect of channel expansion, as the research object, the channel side wall sand particles are used as the research object, the final shape of the channel expansion is determined by the stable state of the particles, the stability of the sand particles is determined by the stress state, and the analysis of the stress balance of the particles In the paper, the relevant concepts and formulas in the river dynamics are cited, the interaction and start-up criteria between the different grain size sand particles are considered, the critical starting speed on the sand particles is calculated by the calculation, the turbulent flow of the flow velocity in the channel, the non-uniform distribution and the water flow in the channel are taken into account. The average flow rate of the channel section is used as the judgment standard for channel expansion. The standard has the characteristics of convenient measurement and easy to use and the like. When the slope of the tip is stable, the channel can be stable, and if the slope of the tip is increased, the channel can not be stable continuously until the penetrating dike Foundation. 2. Experimental study on the development of piping channels, including channel expansion and back-up In the aspect of channel expansion, two model sizes are used to carry out many groups of tests. The results show that the water head difference in the distal end and the channel is small, the seepage force is more obvious to the expansion of the channel, but when the head difference is increased, the penetration force is used to expand the channel. In this paper, the effect of water flow in the channel on the expansion of the channel is more obvious; in the back of the channel, the development of the plane and the cross section of the channel in the back of the channel is studied by two covering layer simulation methods. The results of the test confirm the phase of the tip slope in the mechanism analysis. off content. 3. Numerical simulation of the development of the piping channel, including the channel expansion and the upper In the aspect of channel expansion, based on the two-dimensional finite element seepage process, three criteria of channel cross-section average flow rate, natural repose angle and shape condition are taken as the extension of the extension of the section, and the head difference in the channel and the flow of water in the channel are measured at the distal end and the channel. For the boundary condition, the expansion process of the channel is simulated, and the stable state of the channel is given. On the back of the channel, the calculation of the channel development is carried out by using the quasi-three-dimensional finite element program of the multi-layer water-permeable stratum, and the calculation quantity and the calculation precision are taken into account. The effect substitution method adopts the form of the actual cross section of the channel at the time of the extension and judgment of the cross section of the research channel, and the equivalent rectangular section form is adopted in the calculation of the three-dimensional seepage field, and the flow in the channel and the outside seepage of the channel are consistent before and after the equivalent, and the calculation result shows the seepage field and the through-flow field. The slope of the channel tip can be used to determine if the channel is on the channel On the basis of the program analysis, the development of typical double-layer bank-based piping is verified by comparing the results of the program with the results of the test.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV871;TV223.4

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