重构裂隙网络定量描述方法及各向异性特征研究

Quantitative description methods and anisotropic characteristics of reconstructed DFN model

错综复杂的裂隙网络为岩体渗流提供了主要通道。定量角度表征裂隙网络各向异性特征是裂隙岩体渗流研究的重要基础工作。基于离散裂隙网络重构技术,依托RJNS3D三维裂隙网络重构平台,探讨了离散裂隙网络有效定量描述指标,采用测窗法定量研究了离散裂隙网络的各向异性特征。研究结果表明:裂隙密度、裂隙分维、CI值以及相对无量纲密度四个指标能够较好地定量描述裂隙网络的无序性和连通性;当测窗垂直于具有裂隙平均产状的平面时,易于形成复杂程度较高、连通程度较好的裂隙网络,其定量描述指标明显高于其它方向,呈现出明显的各向异性特征;相对各指标平均值而言,二维裂隙密度差异性系数达到0.111~0.493,裂隙分维差异性系数达到0.015~0.072,CI值差异性系数达到0.007~0.180,相对无量纲密度差异性系数达到0.008~0.724;以往用裂隙分维这一单定量指标描述裂隙网络各向异性特征有所欠缺,选取多指标或者选取差异性最为明显的相对无量纲密度较为合理。工程应用分析表明,裂隙网络重构技术和测窗法的运用能够实现裂隙网络各向异性特征的定量描述,为裂隙岩体渗流特征研究奠定基础。

The complex fracture network of rock mass provides the main paths for fluid transportation. The research on the anisotropic characteristics of fracture network from a quantitative way is an important and fundamental subject. Based on the statistical reconstruction of discrete fracture network and RJNS^(3D), the quantitative description and anisotropic characteristics of fracture network are studied. The results show that:(1) The fracture density, fractal dimension, connectivity index and the relative dimensionless fracture density can quantitatively describe the randomness and connectivity of fracture network.(2) When the measuring window is perpendicular to the average orientation of fractures, a fracture network with a good connectivity can be generated and its quantitative indicates are obviously higher than other directions.(3) Compared with the average values of each index, the difference coefficient of the four indies reaches 0.111~0.493, 0.015~0.072, 0.007~0.180 and 0.008~0.724, respectively.(4) The fractal dimension is not the best index for the description of anisotropic characteristics, and choosing the multi-indicators or the relative dimensionless fracture density can be a good choice. The analysis results of the engineering application show that the method of the DFN reconstruction and measuring window can achieve the quantitative description of the anisotropic characteristics of fracture network. And it may provide some foundations for the study on the percolation characteristics of fractured rock mass.