Enhanced 3D Analysis of Rock Mass Discontinuities: A Novel Approach to Joint Set Spacing Calculation

ABSTRACT: Traces on rock surfaces are a significant data source in spacing calculations. Automated rock mass characterization is becoming increasingly important in rock mechanics, particularly for accurately determining discontinuity spacing. This study utilizes analysis of three-dimensional (3D) digital rock outcrops to completely detect discontinuity data. The research has been integrated into a computer code, enabling efficient analysis of 3D fracture networks, accurate identification of joint sets, and precise computation of set spacing for each joint set. The approach accounts for variations in joint orientation, visible persistence, and scanline location, offering a refined method by merging co-planar planes within each set. The set spacing is computed as the mean distance between adjacent discontinuities. A case study on a real rock outcrop further demonstrates the practical utility of the methodology. The results reveal that non-persistent joint plane assumption leads to higher spacing values compared to fully persistent joints, with the greatest spacing occurring in the Mean Orientation, None-Persistent scenario and the smallest in the Mean Orientation, Full Persistent scenario. Merging co-planar planes, consistently provides a more accurate estimation of set spacing, making this methodology a reliable tool for rock mass characterization in geotechnical engineering.