岩体多裂隙扩展的连续-非连续分析方法

The evolution of initiation, propagation and coalescence of multiple fissures in rock mass is vital to understanding the deformation rules and failure mechanism of rock mass and to evaluating the safety and reliability of geotechnical engineering..Both continua methods and discontinua methods，with the finite element analysis and the discrete element analysis being representive respectively, have their own advantages. Yet both are hard to analyze the failure process from continua to discontinua. Some methods, for example, the extended finite element method, can handle the crack propagation in principle. However, there are still some cruces that need to be solved urgently, like the mesh dependency, the natural extension of multiple fissures, low calculation efficiency, and so on..The discrete element method is installed into the framework of the numerical manifold method to cope with the propagation of multiple fissures, combining, the mesh independence and the utility of contact treatment by Munjiza. The efficiency of contact detection is enhanced by the topological mapping of the block system, leading to a new utility procedure for analyzing the process from continua to discontinua. The proposed method is able to simulate efficiently the natural propagation of multiple fissures, and to overcome the mesh dependence in the like methods. In the end, the proposed method will be employed to simulate dynamically the failure of rock slopes.

研究岩体中多裂隙萌生、扩展及贯通的演化过程对于揭示岩体的变形规律、破坏机理及评价岩土工程的安全可靠性具有十分重要的意义。.以有限元为代表的连续性方法和以离散元为代表的非连续方法都有自己的优势，但二者在分析由连续到非连续的破坏过程时还存在困难。以扩展有限元为代表的分析方法在处理裂纹扩展方面上已取得一定进展，但仍有一些关键问题亟待解决，如网格依赖性、多裂隙自然扩展的模拟、以及计算效率低等问题。.本项研究在数值流形法框架内引入离散元法来处理多裂隙扩展，将流形元的网格无关性和Munjiza接触处理的实效性结合起来，通过块体系统的拓扑映射提高接触检测的效率，发展从连续到非连续演化过程的分析方法。新方法能高效模拟多裂隙的自然扩展，也能克服同类方法中的网格依赖性。最后，将研究成果用于岩质边坡失稳破坏的动态模拟。

本项研究在数值流形法框架内引入离散元法来处理多裂隙扩展，将流形元的网格无关性和Munjiza接触处理的实效性结合起来，通过块体系统的拓扑映射提高接触检测的效率，发展了从连续到非连续演化过程的分析方法。具体研究内容如下：（1）研究势接触力的流形元离散技术，编制、调试接触力算法程序，提出了一种基于统一标定的势接触力计算方法，该方法重新定义了势函数，即三角形单元内一点的势与该点到3条边的最短距离成正比。（2）提出了基于局部单元动态劈裂的FEM/DEM自适应分析方法，以克服裂纹扩展形态对网格的依赖性。（3）为了提高计算效率，研究链表描述块体系统的拓扑映射和直接搜索算法的块体接触检测算法，基于OpenMP多核并行技术实现了有限元-离散元法的并行化。（4）计算方法的前处理设计与计算（粗粒料多边形表征及二维FEM/DEM分析和基于数字图像技术的岩土材料FEM/DEM分析）。（5）计算方法的应用（爆炸气体驱动下岩体破裂的有限元-离散元模拟、模拟水压致裂的二维FDEM-flow方法和基于FDEM-Flow研究地应力对水力压裂的影响）。