JOURNAL OF ROCK MECHANICS

JOURNAL OF ROCK MECHANICS

Calibrating DFN Models with a New Fracture Intensity Measure and Conventional Field Surveys

Document Type : ٍAn English Original Article

Authors
Hamedan University of Technology
10.22034/irsrm.2026.579139.1077
Abstract
Discrete Fracture Network (DFN) models are critical tools in rock engineering for simulating the geometric characteristics of fracture systems. However, accurate DFN modeling is hindered by limitations in conventional survey methods, particularly linear scanlines, which often underrepresent fracture intensity. This study introduces a new metric, the Joint Presence Factor (P), to quantify fracture intensity through planar sampling. The metric represents the percentage of sampling apertures intersected by fractures on a survey plane, providing a dimensionless measure of fracture occurrence that is practical, spatially representative, and physically intuitive, while also being simpler to measure and interpret than established fracture intensity indices. Alongside the field calculation of P in a case study, this metric was also calculated within DFN models through a custom FISH code. Using response surface methodology, the key DFN parameters, including fracture length, scaling exponent, and frequency, were optimized within the proposed calibration framework to align the model-derived P with field observations. The results demonstrated that the initial DFN model underestimated fracture intensity (P = 14%) compared to field measurements (P = 21%), reflecting the limitations of scanline surveys. After calibration, the optimized model yielded P = 20%, showing good agreement with field data. The results indicated that adjusting fracture length distribution and intensity improves the representation of smaller fractures and enhanced overall network density, thereby increasing the reliability and accessibility of DFN models for rock engineering applications.
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