Mixture distribution model for three-dimensional geometric attributes of multiple discontinuity sets based on trace data of rock mass

• Published in: Engineering geology 2022-12, Vol.311, p.106915, Article 106915
• Main Authors: Zhang, Qi, Wang, Xiaojun, Zhu, Hehua, Zhang, Keshen, Li, Xiaojun
• Format: Article
• Language: English
• Subjects: Discontinuous rock mass; Discrete fracture network; Geological coordinate system; Geometric probabilistic relationship; Mixture distribution model
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2022.106915

The geometric attributes of discontinuities are critical to an accurate discrete fracture network (DFN) model of rock mass. It is difficult to estimate three-dimensional (3D) geometric parameters of multiple groups of discontinuities by observation data. The study proposes a mixture distribution model for the 3D geometric attributes of multiple discontinuity sets. The method of estimating the mixture distributions of 3D geometric attributes of all discontinuity sets from the two-dimensional (2D) trace data in a sampling window is established and modified, including discontinuity diameter distribution estimation, volume density estimation, orientation distribution estimation, and distribution mixing. Discontinuities are assumed to be thin disks uniformly distributed in space, and their roughness and aperture are ignored. Discontinuity diameter and orientation follow lognormal distribution and bivariate normal distribution, respectively. Orientation distributions defined on the definitional domain of the geological coordinate system are derived to represent the real frequency distributions of orientation measurements in 3D rock mass space. The mixture distribution model is verified by using Monte Carlo method to generate DFNs with different volume densities, and distribution parameters of orientation and diameter. The maximum error of volume density is