Three Dimensional Analysis of Seepage Through Fill Dam for Irrigation Using the Isoparametric Finite Elements

在堆石坝的规划设计和施工中，坝体内渗流或坝基渗漏是一个重要问题。由于堆石坝的经济和安全性能，有必要对堆石坝及其地基中的渗流量进行计算。本文的研究结果如下：1.渗流问题采用稳态渗流。2在这种情况下，可以采用Nenman(1973)提出的饱和-非饱和有限元方法。利用牛顿-拉夫森迭代算法得到一个近似的浸润面，因为浸润面上的压力必须为零，因为它暴露在大气中。3用三维等参元的形状，说明了未知变量Phi的变化。4利用稳态流动的天平写出控制方程，并在试探函数展开的假设下进行有限元离散，使用控制方程的弱公式或泛函的变分陈述来最小化原始问题的满意度。5一个计算机程序，执行大量的同时，用FORTRAN编程语言编写了高斯消去法求解的线性代数方程。6在本文中，渗透率识别过程基于输出误差准则，迭代地改进现有的渗透率系数估计，直到计算的潜水面与测量的输出足够接近。

With regard to planning design and construction of fill dam, Seepage within the dam body or through the foundation are one of important problems. Because of economical and safe performance of fill dams, it is needful to compute quantities of seepage flow in fill dams and their foundations.The results of this research are as follows.1 Steady state flow was dealt with in this seepage problem.2 In this case, a saturated-unsaturated finite element approach, as proposed by Nenman (1973), could be applied. The Newton-Raphson iteration algohithm is also used to obtain an approximate phreatic surface, because the pressure must be zero on the phreatic surface as this is exposed to atmosphere.3 With the shape of the three-dimensional isoparametric element, the variation of the unknown, phi, had been specified.4 The governing equation was written by the balance for steady-state flow and the finite element discretization was proceeded on the assumption of a trial function expansion, using either the week formulation of the governing equation or the variational statement of the functional giving on minimization the satisfaction of the original problem.5 A computer program to carry out a large set of simultaneous, linear algebraic equation solved by Gauss elimination was coded with FORTRAN programming language.6 In the paper, permeability identification procedure was based upon an output error criterion where an existing estimate of the coefficient of permeability was iteratively improved until the calculated phreatic surface was sufficiently close to that of the measured output.