Clogging of toe drain drastically affects phreatic seepage in earth dams

IF 4 2区 环境科学与生态学 Q1 WATER RESOURCES
Shahad Al-Yaqoubi , Ali Al-Maktoumi , Yurii Obnosov , Anvar Kacimov
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Abstract

In aged levees, toe (blanket) drains get clogged with time due to seepage-induced suffusion and translocation of fine soil fractions from the upstream to the downstream part of the embankment. These particles deposit on the top of the drain (usually, Terzhagi's graded gravel) as a cake. Also, high hydraulic gradients in the vicinity of the drain move the fine particles into the body of the coarse filter material such that “internal colmation” takes place. In this paper 2-D seepage to a clogged drain is studied experimentally, analytically and numerically. In a sandbox, we illustrate the difference in the position of a phreatic surface and the seepage flow rate between an equipotential toe drain and a clogged one. In the analytical solution, a potential flow model is used and the Neumann (Kirkham-Brock) boundary condition on the clogged drain surface (horizontal segment) is imposed. A circular triangle is mapped conformally onto a reference half-plane, where Hilbert's boundary value problem for a holomorphic function is solved. For a given size of the levee, clogging causes a significant rise of the phreatic surface, although the seepage flow rate drops. In HYDRUS2-D simulations, a FEM-meshed Richards’ equation for a saturated-unsaturated 2-D flow is used for solving in a composite polygon, which mimics a vertical cross-section of a rectangular levee and a clogged-colmated blanket drain. Numerical results are in rough agreement with the analytical model.

坝趾排水沟的堵塞会严重影响土坝的噬水渗流
在老化的堤坝中,堤趾(毛毯)排水沟会随着时间的推移而堵塞,这是由于渗水引起的淤积以及细土碎屑从堤坝上游向下游的转移。这些颗粒会像滤饼一样沉积在排水沟的顶部(通常是特尔扎基分级砾石)。此外,排水沟附近的高水力梯度会将细颗粒移动到粗滤料体内,从而产生 "内部胶结"。本文对堵塞排水沟的二维渗流进行了实验、分析和数值研究。在沙箱中,我们说明了等势排水沟和堵塞排水沟之间的噬水表面位置和渗流速率的差异。在分析求解中,我们使用了势流模型,并在堵塞的排水沟表面(水平段)施加了诺依曼(柯克姆-布洛克)边界条件。一个圆形三角形被适形地映射到一个参考半平面上,在这个半平面上求解全形函数的希尔伯特边界值问题。在堤坝尺寸一定的情况下,虽然渗流率下降,但堵塞会导致堰塞面显著上升。在 HYDRUS2-D 模拟中,饱和-非饱和二维流的有限元网格理查兹方程用于在一个复合多边形中求解,该多边形模拟了矩形堤坝和堵塞-沉积毛毯排水沟的垂直横截面。数值结果与分析模型基本一致。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Advances in Water Resources
Advances in Water Resources 环境科学-水资源
CiteScore
9.40
自引率
6.40%
发文量
171
审稿时长
36 days
期刊介绍: Advances in Water Resources provides a forum for the presentation of fundamental scientific advances in the understanding of water resources systems. The scope of Advances in Water Resources includes any combination of theoretical, computational, and experimental approaches used to advance fundamental understanding of surface or subsurface water resources systems or the interaction of these systems with the atmosphere, geosphere, biosphere, and human societies. Manuscripts involving case studies that do not attempt to reach broader conclusions, research on engineering design, applied hydraulics, or water quality and treatment, as well as applications of existing knowledge that do not advance fundamental understanding of hydrological processes, are not appropriate for Advances in Water Resources. Examples of appropriate topical areas that will be considered include the following: • Surface and subsurface hydrology • Hydrometeorology • Environmental fluid dynamics • Ecohydrology and ecohydrodynamics • Multiphase transport phenomena in porous media • Fluid flow and species transport and reaction processes
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