岩体结构面各向异性变异系数的尺寸效应研究

岩体结构面的各向异性与尺寸效应特征对其力学性质影响较大，综合考虑两者之间的相互关系对工程岩体稳定性评价具有重要意义。全面分析不同尺度结构面的各向异性分布，提出考虑正交方向三维形貌参数的各向异性变异系数AVC3D。通过渐进覆盖法统计4组天然岩体结构面10种不同采样尺寸的各向异性变异系数及其尺寸效应规律。结果表明：各向异性变异系数均随结构面尺寸增大而减小至定值，其与结构面尺寸具有较好的负对数函数关系；通过归一化处理，各向异性变异系数与结构面尺寸呈现较好的线性函数关系，表明各向异性变异系数具有分形结构，分维数D可以实现其尺寸效应的规律统计。该方法揭示了影响结构面形貌特征方向性变化的最大有效倾角 和粗糙系数C的增长幅度会随采样尺寸增大趋于稳定的变化机制，体现了当结构面达到各向异性尺寸效应的阈值后，会呈现出稳定的各向异性规律。

Study of size effect on the anisotropic variation coefficient of rock joints

The anisotropy and size effect of a rock joint have a great influence on its mechanical properties. Considering the relationship between these two features is of great significance to the evaluation of rock mass stability. In this study, in order to investigate the anisotropic distribution of rock joints at different scales, the anisotropic variation coefficient AVC3D is proposed which considers the three-dimensional morphology parameter of orthogonal directions. The AVC3D of four natural joints at ten different sampling sizes are measured based on the progressive coverage statistical method, and the size effect law of the AVC3D is obtained. The conclusions are as follows: the AVC3D reduces to stable with the increase of the rock joint size, and there is a good negative logarithm function relationship between them. The normalized statistical average values of the AVC3D and the normalized size of the rock joints show a good linear function, indicating that the AVC3D has a fractal structure. The fractal dimension D can be achieved using the regular statistics of the size effect of the AVC3D. This method reveals the mechanism that the maximum effective dip angle and the roughness coefficient C, which affect the directional change of the structural surface features, tend to be more stable with the increase of sampling size. It shows that once the rock joint reaches the threshold of the anisotropic size effect, the stable anisotropy will appear.