不连续岩体渗流的复合单元法初步研究

PRELIMINARY RESEARCH ON COMPOSITE ELEMENT METHOD FOR SEEPAGE PROBLEMS IN DISCONTINUOUS ROCK MASSES

基于复合单元法的原理,提出了不连续岩体三维渗流的新算法。该算法具有以下3个主要特点:(1)不连续面(如断层或节理)含于复合单元之中,在划分网格时不予考虑,使网格的生成大大简化;(2)复合单元中可含有由不连续面分割而成的任意形状的子单元,每个子单元各有一组用于插值的映射节点水头。子单元的水头势、流速由相应映射节点水头计算得到,而复合单元中不连续面上的水头势、流速则由其相邻的2个子单元的映射节点水头计算得到;(3)复合单元中映射子单元的节点水头求解过程与传统有限元法类似,不含不连续面的单元自动退化为常规有限单元,因而复合单元法计算程序可以方便地与传统有限元分析程序融合。简单模型算例验证了该算法的正确性,而重力坝算例则表明该算法的有效性和在前处理上的优越性。

Based on the principle of composite element method, a new algorithm for the three-dimensional seepage problem in discontinuous rock masses is presented. The three leading features of this algorithm are as follows： （1） discontinuities segments such as faults and joints are contained in the composite elements, thus the mesh generation of discontinuous rock masses will not be restricted by the number, position and orientation of the discontinuities and can be considerably simplified. The quantity of mesh can be easily controlled; and the shape of mesh can be . improved correspondingly; （2） being dissected by the discontinuities, the composite elements may contain sub-elements of arbitrary shape. The hydraulic potential in sub-elements are interpolated from their corresponding mapping nodal hydraulic potential, respectively. With the solved mapping nodal hydraulic potential, the velocity, flow rate in each sub-dement can be calculated： and those in discontinuities segments are calculated from the two sets of mapping nodal hydraulic potential of their neighboring sub-elements; （3） in composite element method, the solving procedure of the mapping nodal hydraulic potential is similar to that in conventional finite element method, andthe elements containing no discontinuities are degenerated to conventional finite elements automatically. Thus the programs for composite element algorithm can be incorporated into the conventional finite element analysis procedure with intrinsic coherence. The comparative study between the composite dement method and the conventional finite element method for seepage problem has been implemented with two simple models and. a gravity, dam example, respectively; and the validity and effectiveness of this new algorithm are verified by the given examples.