基于三维裂隙连通率的裂隙岩体表征单元体研究

STUDY OF REPRESENTATIVE ELEMENTARY VOLUME FOR FRACTURED ROCK MASS BASED ON THREE-DIMENSIONAL FRACTURE CONNECTIVITY

三维裂隙连通率综合反映了岩体内裂隙发育特征,是评价工程岩体稳定性的一个重要参数。为合理选取具有代表性的裂隙连通率,基于投影法对水平向三维裂隙连通率的尺寸效应进行分析研究,进一步确定岩体表征单元体尺寸。首先,对实测裂隙数据进行几何参数统计分析,采用逆建模方法建立一个100 m×100 m×140 m的裂隙网络模型。在模型中的10个不同高程上设置水平向的投影基准面,基准面尺寸位于5 m×5 m^100 m×100 m范围。利用投影法计算各投影基准面的三维裂隙连通率,分析三维裂隙连通率随研究尺度的变化情况。采用T检验和F检验判定各级尺寸与最大研究尺寸的研究区域的连通率均值和方差是否存在显著差异。研究结果表明,当研究尺寸达到65 m×65 m时,连通率均值和方差进入稳定状态,该尺寸可视为研究岩体水平方向的表征单元体。

Three-dimensional(3D) fracture connectivity,which can comprehensively reflect the fracture features, is a key parameter for evaluating the stability of engineering rock masses. For the purpose of determining a representative 3D connectivity value,the scale effect of 3D connectivity is investigated based on projection method and the representative elementary volume(REV) of the study rock mass is further estimated. First,fracture data collected from an exploration tunnel are statistically analyzed and used to generate a large discrete fracture network of 100 m×100 m×140 m by an inverse method. Inside the fracture network,reference planes with different sizes ranging from 5 m×5 m to 100 m×100 m are sampled 10 times on different elevations. A projection method is adopted to calculate horizontal 3D fracture connectivity of each reference plane and the relationship between the 3D fracture connectivity value and the study domain size is analyzed. The REV of the rock mass is estimated based on a series of T-tests and F-tests. The T-tests and F-tests are performed to determine whether the mean value and variance of fracture connectivity for different sizes are statistically equal to the largest size, respectively. The results show that a size of 65 m×65 m could be viewed as the REV,beyond which the mean value and variance of the connectivity converge to a stable state.