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The impact of fracture-matrix interaction on thermal-hydrological conditions in heated fractured rock

Jens T. Birkholzer and Yingqi Zhang
The impact of fracture-matrix interaction on thermal-hydrological conditions in heated fractured rock
Vadose Zone Journal (May 2006) 5 (2): 657-672


Dual-continuum models have been widely used in modeling flow and transport in fractured porous rocks. Among many other applications, dual-continuum approaches were used in predictive models of the thermal-hydrological conditions near emplacement tunnels (drifts) at Yucca Mountain, NV, the proposed site for a radioactive waste repository in the USA. In unsaturated formations such as those at Yucca Mountain, the magnitude of mass and heat exchange between the two continua--fracture network and rock matrix--depends on the small-scale flow characteristics in the fractures, because channelized finger-type flow strongly reduces the interface area between the matrix surfaces and the flowing liquid. This effect may have important implications, for example, during the time period that the fractured rock near the repository drifts would be heated above the boiling point of water. Depending on the magnitude of heat transfer from the matrix, water percolating down the fractures will either boil off in the rock region above drifts or may penetrate all the way to the drift walls and possibly seep into the open cavities. In this study, we conducted a sensitivity analysis using different approaches to treat fracture-matrix interaction in a three-dimensional dual-continuum setting. Our simulation example was a laboratory heater experiment described in the literature that provides evidence of rapid water flow in fractures, leading to seepage into the heater hole despite above-boiling conditions in the adjacent fractured rock. We showed that the experimental finding can only be reproduced when the interface area for heat transfer between the matrix and fracture continua is reduced to account for flow channeling. Our analysis also suggests that the conditions in the laboratory experiment are unique and not representative of the expected thermal-hydrological conditions near emplacement drifts at Yucca Mountain.

ISSN: 1539-1663
Serial Title: Vadose Zone Journal
Serial Volume: 5
Serial Issue: 2
Title: The impact of fracture-matrix interaction on thermal-hydrological conditions in heated fractured rock
Affiliation: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA, United States
Pages: 657-672
Published: 200605
Text Language: English
Publisher: Soil Science Society of America, Madison, WI, United States
References: 33
Accession Number: 2006-056717
Categories: Environmental geologyEngineering geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. 2 tables
N36°43'60" - N37°00'00", W116°34'60" - W116°25'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Soil Science Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200631
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