柱状节理岩体细观破坏机理的扩展边界元法研究

Plenty of columnar jointed rock mass have been discovered with the development of hydropower in southwest China, which contains three sets of multi-scale joints with different distribution densities, growth levels and mechanical properties: through joints between columns (m level), steeply-dipping (dm level) and gently-dipping joints (cm level) inside columns. However, the columnar jointed rock mass is simplified as an anisotropic constitutive model based on the equivalent theory in most of current research. In this project, an equivalent joint network model is generated to simulate the evolution of multi-scale joint sets through statistical analysis of joints distribution. The partition unit method is introduced into conventional dual boundary element method to construct multi-crack enriched functions, and a new cohesive joint fissure model is proposed to develop an extended boundary element program to simulate the evolution of multi-scale joint sets inside columnar jointed rock mass. Some classical examples and physical model tests are adopted to modify the program, and the back analysis of exaction process is carried out, on the base of site monitoring data for Baihetan hydropower station, to investigate the influence of geometry parameters, such as the dip angle, trace length, connectivity and joint surface strength, which will provide an important guideline for the design and construction of underground caverns in columnar jointed rock development area.

随着我国西南水电事业的发展，大量的柱状节理岩体相继揭露，其内部包含三组分布密度、发育程度和力学性质各异的多尺度节理组：柱间贯通节理（米级）、柱内陡倾角节理（分米级）和缓倾角节理（厘米级）。目前对柱状节理岩体的研究大多基于宏观等效思想，将其概化为各向异性本构模型，本项目拟通过现场节理分布规律统计分析，生成与原岩体等效的随机节理网络模型，在传统对偶边界元法的基础上引入单元分解思想，构造复合多裂纹裂尖单元加强函数，建立粘聚接触节理裂隙模型及相应的起裂准则和止裂判据，开发一套适用于模拟柱状节理岩体内多尺度节理细观演化过程的扩展边界元法程序。利用典型算例和物理模型试验对程序进行验证和完善，结合已有白鹤滩水电站现场监测资料对开挖过程进行反演分析，探讨多尺度节理几何分布（如倾角、迹长、连通率等）及节理面强度对柱状节理岩体工程力学特性的影响，为柱状节理岩体发育地区地下洞室设计和施工提供重要的指导作用。

随着我国西南水电事业的发展，大量的节理岩体相继揭露。本项目开发了一套适用于裂隙岩体内多尺度节理岩体细观演化过程的对偶边界元法计算程序，为了更加准确的捕捉裂尖应力集中现象，构建了新型奇异裂尖单元形函数，同时重点考虑了扭曲单元奇异积分的精确计算问题，提出了保形变换预处理方案，实现了不同裂纹网格离散形式的精确计算；在Oda裂隙张量的基础上，综合考虑了节理系统的变形特性，提出了节理变形张量，实现了节理系统空间几何和变形特性的单一参量表征，为节理岩体抗变形能力和空间各向异性变形特征的评价提供了理论基础；根据白鹤滩左岸坝基柱状节理岩体结构特征的现场调查和测量结果，采用节理变形张量理论和各向异性变形评价指标详细分析了白鹤滩左岸坝基柱状节理岩体的空间各向异性变形特征，分析结果表明白鹤滩左岸坝基柱状节理岩体具有近似横观各向同性的空间变形特性，并进一步验证了节理岩体张量变形本构模型的合理性。