Stochastic fracture geometry modeling in 3-D including validations for a part of Arrowhead East Tunnel, California, USA

Pinnaduwa H.S.W. Kulatilake, Jeong Gi Um, Mingyu Wang, Richard F. Escandon, John Narvaiz

Research output: Contribution to journalArticlepeer-review

71 Scopus citations

Abstract

Eight-hundred and fifty nine fractures of a gneissic rock mass were mapped using 16 scanlines placed on steep rock exposures that were within 300 m of a tunnel alignment before the tunnel excavation. These data were analyzed using the software package FRACNTWK to find the number of fracture sets that exist in the rock mass, 3-D fracture frequency for each set and the probability distributions of orientation, trace length, fracture size in three dimensions (3-D) and spacing for each of the fracture sets. In obtaining these distributions corrections were applied for sampling biases associated with orientation, trace length, size and spacing. Developed stochastic 3-D fracture network for the rock mass was validated by comparing statistical properties of observed fracture traces on the scanlines with the predicted fracture traces on similar scanlines. The one-dimensional (1-D) fracture frequency of the rock mass in all directions in 3-D was calculated and is presented in terms of a stereographic plot. The 1-D fracture frequency along the tunnel alignment direction was predicted to be about 6.5 fractures/m before the tunnel excavation. This prediction was found to be in excellent agreement with the observed values obtained about 1 year later during the tunnel excavation. This was another validation conducted for the developed 3-D fracture network.

Original languageEnglish (US)
Pages (from-to)131-155
Number of pages25
JournalEngineering Geology
Volume70
Issue number1-2
DOIs
StatePublished - Oct 2003

Keywords

  • Case study
  • Fracture geometry
  • Fracture network validation
  • Probability distributions
  • Statistical modeling
  • Tunnel site

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

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