北山花岗岩深部节理间距分布多重分形研究

岩体节理几何特征定量描述是岩体力学性质和渗透性研究的基础，更是核废料处置库场址筛选和评价过程的主要内容。基于甘肃北山高放废物深地质处置库预选区BS17、BS18和BS19钻孔岩芯节理数量修正数据，针对节理间距建立了类负指数分布数学统计模型，进一步应用于RQD体系定量评价深部岩体完整性，通过与RID体系对比验证了概率模型的可靠性。指出节理数量-间距关系具有明显的分段线性特征，分维数随着间距增大而增大。确定了节理间距-数量关系符合尺度律，得出了数量与间距关系的多重分形特征。进一步分析了数量与埋深的多重分形特征，初步实现了岩芯节理的定量描述。验证了多重分形谱可以很好地统计分形维特征，尤其是节理几何形状及分布特征。该研究结果可为实现基于钻孔岩芯节理几何特征数据的深部岩体节理三维网格模拟提供参考。

Multi-fractal characteristics of joint geometric distribution of granite in Beishan

Quantitative determination and explanation for geometric characteristics of joints in deep rock mass are fundamental to investigate mechanical properties and permeability, and in particular they are the main factors to determine the site of nuclear waste reserve and evaluation. Based on the modified data of joint number from three boreholes of BS17, BS18, BS19 in Beishan, Gansu province, a negative exponential-like distribution mathematical model is established. Furthermore the model is applied to evaluate the integrity of deep rock mass in rock quality designation (RQD) system. The reliability of the model is verified by comparing with rock integrity designation (RID) results. It should be pointed out that there is a piecewise function of a linear relationship between the joint number and spacing, and the fractal dimension increases with the spacing expanding. According to the power-law between the joint number and spacing, there is a multi-fractal relationship between them, as well as the joint number and depth. The multi-fractal spectrum is suggested to analyze the statistical data of joint geometric shape and distribution. The results provide a reference for 3D simulation of joints in deep rock mass based on geometrical characteristics of borecore joints.