摘要
非连续变形分析法(DDA)的线性位移模式,仅能描述常应变块体单元,实际应用中往往显得不够精确,有时甚至会引起很大的误差。为此近来先后引进诸多改进方法,如直接提高块体位移模式的阶数、在块体内部划分子块体并增设节理单元以及采用有限元插值等,也都存在缺陷。无网格法具有许多有效的插值模式,尝试引进无网格迦辽金中采用的移动最小二乘法(MLS)插值,来表达块体位移及应力场,为此在块体内布置离散的插值节点,用MLS建立块体内任意点位移近似函数代替原DDA位移表达式,并遵循原DDA的一些基本过程,包括:根据能量极值原理建立平衡方程、隐式求解、按时间步迭代统一求动静力问题、根据开合迭代模式检查可能接触类型等。数值算例表明,耦合无网格法的DDA能有效计算块体应力场,对块体系统的计算结果明显优于原线性位移模式。
The linear displacement function of discontinuous deformation analysis(DDA) is a complete first-order polynomial,which can only describe block element with constant strain,and in practice,it cannot provide required precision and sometimes will cause large errors. Recently,some improvements are developed such as the direct usage of the displacement function with higher-order polynomials,sub-blocks with additional artificial joint sets along the border,and the block-finite-element displacement mode,etc However,all these have their own defects. As the meshfree methods have many efficient interpolation modes,the moving least squares(MLS) procedure commonly adopted in the element free Galerkin(EFG) method can be used to describe displacement and stress field. Hence,new interpolation nodes are inserted into the blocks and their borders,and any point in a block has a new displacement expression by MLS interpolation of nodal displacements of the block,and the basic procedures of the original DDA are presented including building the simultaneous equilibrium equations according to energy extremum theory,implicitly solving unknown variables,using time-step iteration procedures to solve uniformly dynamic or static problems and open-close iteration procedure to search for possible contact types,etc The numerical examples indicate that the proposed scheme can efficiently simulate block stress field;and the results are obviously better than those of linear mode DDA.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2007年第S2期4195-4201,共7页
Chinese Journal of Rock Mechanics and Engineering
关键词
岩石力学
非连续变形分析法
无网格法
位移模式
移动最小二乘法
rock mechanics
discontinuous deformation analysis(DDA)
meshfree method
displacement mode
move least square(MLS) method
