Estimating large-scale fractured rock properties from radon data collected in a ventilated tunnel

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To address regulatory issues regarding worker safety, radon gas concentrations have been monitored as part of the operation of a deep tunnel excavated from a highly fractured tuff formation. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured rock. An iTOUGH2 model was developed to predict radon concentrations for prescribed ventilation rates. The numerical model was used (1) to estimate the permeability and porosity of the fractured formation at the length scale of the tunnel and extending tens of meters into the surrounding rock, and (2) to ... continued below

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Unger, Andre; Finsterle, Stefan & Bodvarsson, Gudmundur S. May 12, 2003.

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To address regulatory issues regarding worker safety, radon gas concentrations have been monitored as part of the operation of a deep tunnel excavated from a highly fractured tuff formation. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured rock. An iTOUGH2 model was developed to predict radon concentrations for prescribed ventilation rates. The numerical model was used (1) to estimate the permeability and porosity of the fractured formation at the length scale of the tunnel and extending tens of meters into the surrounding rock, and (2) to understand the mechanism leading to radon concentrations that potentially exceed the regulatory limit. The mechanism controlling radon concentrations in the tunnel is a function of atmospheric barometric fluctuations propagated down the tunnel. In addition, a slight suction is induced by the ventilation system. The pressure fluctuations are dampened in the fractured formation according to its permeability and porosity. Consequently, as the barometric pressure in the tunnel drops, formation gases from the rock are pulled into the opening, resulting in high radon concentrations. Model calibration to both radon concentration data measured in the tunnel and gas phase pressure fluctuations observed in the formation yielded independent estimates of effective, large-scale fracture permeability and porosity. The calibrated model was then used as a design tool to predict the effect of adjusting the ventilation-system operation strategy for reducing the probability that radon gas concentrations will exceed the regulatory limit.

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OSTI as DE00822801

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  • TOUGH Symposium 2003, Berkeley, CA (US), 05/12/2003--05/14/2003

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  • Report No.: LBNL--52501
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 822801
  • Archival Resource Key: ark:/67531/metadc785528

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • May 12, 2003

Added to The UNT Digital Library

  • Dec. 3, 2015, 9:30 a.m.

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  • April 4, 2016, 5:55 p.m.

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Unger, Andre; Finsterle, Stefan & Bodvarsson, Gudmundur S. Estimating large-scale fractured rock properties from radon data collected in a ventilated tunnel, article, May 12, 2003; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc785528/: accessed September 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.