摘要
在无压渗流分析中,需要确定渗流自由面(二维渗流分析时为浸润线,三维渗流分析时为浸润面)的位置。所谓自由面是指其位置可以随着降雨、蒸发等因素的影响而自由变动；自由面上的压力为大气压。存在于自然界中的很多渗流现象都具有自由面,如坝体渗流、各种闸坝的绕坝渗流等。虽然此时渗流控制方程是线性的,但由于部分渗流区域边界(渗流自由面)是未知的,在渗流分析时需同时确定,使得这类问题变为非线性问题。
本文基于连续介质和非连续介质(岩体裂隙网络)渗流理论,对渗流区域非线性问题进行了研究,主要完成了以下几个方面的工作：
1.讨论了连续介质渗流和非连续介质(岩体裂隙网络)渗流的基本概念、渗流的运动规律、渗流场满足的基本方程及定解条件；讨论了利用有限单元法实施渗流分析的步骤,尤其针对单元的选择与插值函数的建立、渗流问题的变分原理、有限单元计算公式的推导、渗透矩阵的形成等实施步骤中的重要环节作了详细的阐述。
2.对确定渗流区域边界的数值方法进行总结和归类,并对各种方法的优点和缺点进行了比较。
3.在移动网格法的基础上,以渗透矩阵调整法为主线,经单元渗透矩阵调整法,最终将复合单元高斯点法应用于求解连续介质渗流区域非线性问题；相应地应用可视化编程工具Digital Visual FORTRAN 6.0,通过内嵌的Microsoft Developer Studio可视化集成开发环境,采用FORTRAN 90语言自主开发了二维、三维无压渗流分析有限元程序。
4.针对三维裂隙网络渗流理论,编制了求解线性问题的相应程序；给出了利用复合单元高斯点法求解岩体裂隙网络渗流区域非线性问题的实施步骤,为深入研究该问题奠定了基础。
5.将自己编制的三维无压渗流分析有限元程序应用于某尾矿坝的渗流分析中,通过与实测资料进行对比,进一步验证了程序的可行性。
Seepage free surface is a saturation line in the two-dimensional analysis,and is a surface in the three-dimensional analysis.The so-called free surface refers to that its location can be changed in freedom as rainfall, evaporation and other factors, and its pressure is the atmospheric pressure.The free surface can be found in many phenomenon, which exist in the nature,like seepage through the dam and seepage around the sluice or dam. Although the seepage differential equations at this time are linear, because some of the regional border (seepage free surface) is unknown in the seepage analysis and must be determined simultaneously, making this type of problem a non-linearity problem.
This paper carrys out a major study of seepage with free surface on continuous media,and conducts a preliminary study of the seepage with free surface on rock fracture network. The main aspects are as follows:
1. This paper discusses the basic concept of seepage on continuous media and rock fracture network,including the movement of seepage and the basic equations and boundary conditions which used in seepage field, etc.At the same time,it discusses the steps of implementing seepage analysis using the basic principles of finite element method. In particular, those important aspects in the implementation such as the choice of unit and the establishment of interpolation function, the variational principle of seepage problem,the deduction of the formula for finite element method and the formation of infiltration matrix are elaborated.
2. Meanwhile,this paper mades an summary and classification about numerical methods of determining the seepage free surface,whose strengths and weaknesses are detailed also.
3.Based on calculating seepage with the method of mobile grid,a kind of fixed grid method—method with changing conductivity matrix is used in unconfined seepage analysis. From the method with changing element conductivity matrix, finally,composite element gauss points method is applied for caculating seepage with free surface on continuous media.At the same time,a two-dimensional、three-dimensional finite element method program for unconfined seepage analysis by FORTRAN 90 has been developed,using the software of Digital Visual FORTRAN 6.0 in the enviroment of Microsoft Developer Studio.
4.A FEM program which is used to calculate the linearity problem of seepage on rock fracture network has been developed.Meanwhile,implementation steps of caculating the nonlinear problem in seepage region on rock fracture network with the method of Composite Element Gauss point is given.
5.The self-developed FEM program for unconfined seepage analysis is used to calculate the seepage field of a project example.Through comparison with the measured data, the feasibility of the procedure is further verified.
引文
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