岩体边坡失稳问题损伤断裂演化过程分析的自适应多尺度数值模拟研究

The impetus to the project comes from the engineering geologic disasters, such as landslide, dam break etc. A adaptive multiscale numerical method coupling the discrete element method for fracture analysis and the finite element method for damage analysis, is developed, so as to simulate the generation and evolution of rock fractures and the fracturing failure through the slope. The finite element method simulation based on the continuum model and damage mechanics, covers the whole medium for the simulation, while the localized rock fracturing region is modeled with the discrete particle assembly and numerically simulated with the discrete element method. In the process of generation and evolution of rock fracture, the region numerically simulated with the discrete element method is enlarged, to make sure the whole rock fracturing region is completely covered by the discrete element simulation. Therefore, the whole evolutionary process from the localized rock fracture to the fracturing failure through the slope may be simulated. The present adaptive multiscale numerical method not only greatly enhances the computational efficiency, but also is capable of simulating microscopic uncontinuous failure phenomena occurring in the evolutionary process of rock damaging and fracturing failure, and illustrating the mechanism of microscopic failure. With the comparison between the numerical results obtained by the multiscale simulation and the results obtained by the large centrifuge mechanical experiment simulation, the availability and applicability of the proposed multiscale method is illustrated. Moreover, the multiscale numerical simulation and the large centrifuge mechanical experiment simulation are combined with each other to study influential factor, causative mechanism and the mode of deformation and fracturing failure of the rock slope.

以山体滑坡、溃坝等工程地质灾害为背景，发展模拟边坡内岩体裂缝生成、扩展以及边坡贯穿性断裂破坏的耦合断裂分析离散元法和损伤分析有限元法的自适应多尺度分析方法。将基于连续体模型的损伤力学有限元法模拟覆盖边坡的计算全域，对岩体开裂的局部区域采用散粒集合体模型，进行离散元法模拟，在岩体裂缝不断生成和扩展的过程中，相应地扩大离散元模拟区域的范围，保证离散元法计算能够覆盖全部的岩体开裂区域，以模拟岩质边坡的局部开裂到整体贯穿性断裂破坏的过程。此自适应多尺度数值模拟算法将不仅具有在计算效率上的高效性，而且能够即时地捕捉岩体在损伤断裂破坏的演化过程中的细观非连续性破坏现象并揭示其细观破坏机理。将岩体边坡溃滑灾害的多尺度数值计算结果和大型离心机试验模拟结果相对比，论证所发展的多尺度方法的有效性和适用性。并且将多尺度数值模拟结合大型离心机试验模拟，进一步研究岩体滑坡灾害的影响因素、形成机理及变形破坏机制模式。

在岩石的破坏过程中，岩石内小尺度的天然微裂缝通过扩展贯通发展为大尺度的贯穿性破坏裂缝。岩石断裂破坏具有微裂缝损伤向大裂纹断裂的发展演化过程。本项目以大型水电站建设的岩体边坡为工程背景，基于连接尺度方法的离散元和有限元的耦合计算框架，本文发展了耦合损伤力学有限元方法和断裂力学颗粒离散元方法的连接尺度方法，以此模拟岩石破坏的断裂损伤耦合过程。在细观尺度上，采用颗粒间的细观胶结接触模型和光滑节理模型，模拟岩石宏观大尺度裂缝发展的断裂过程。修正现有的统计损伤本构模型，分别针对拉剪和压剪损伤状态采用相应不同的本构模型及模型参数定义。给出修正的统计损伤本构模型参数的拟合计算过程。开展岩石三轴压缩卸荷声发射试验，测定岩石在开挖卸荷工况下的三轴抗压强度指标，获得相应的岩石物理力学参数，为后期岩体边坡工程计算的开展提供依据。并根据岩石试验数据、工程现场监测数据与数值模拟结果的对比，说明所发展的模型和数值方法的有效性。

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