Geophysical tomography for imaging water movement in welded tuff
Alterant tomography has been evaluated for its ability to delineate in-situ water flow paths in a fractured welded-tuff rock mass. The evaluation involved a field experiment in which tomographs of electromagnetic attenuation factor (or attenuation rate) at 300 MHZ were made before, during, and after the introduction to the rock of two different water-based tracers: a plain water and dye solution, and salt water and dye. Alterant tomographs were constructed by subtracting, cell by cell, the attenuation factors derived from measurements before each tracer was added to the rock mass from the attenuation factors derived after each tracer was added. The alterant tomographs were compared with other evidence of water movement in the rock: borescope logs of fractures, and postexperiment cores used to locate the dye tracer on the fractured surfaces. These comparisons indicate that alterant tomography is suitable for mapping water flow through fractures and that it may be useful in inferring which of the fractures are hydrologically connected in the image plane. The technique appears to be sensitive enough to delineate flow through a single fracture and to define fractures with a spatial resolution of about 10 cm on an imaging scale of a few meters. 9 refs., 3 figs.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 59945
- Report Number(s):
- UCRL-95078; CONF-860930-1; ON: DE86016003
- Resource Relation:
- Conference: Annual information meeting of the Canadian Nuclear Fuel Waste Management Program, Winnipeg (Canada), 7-12 Sep 1986; Other Information: PBD: 1 Sep 1986
- Country of Publication:
- United States
- Language:
- English
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Preliminary evaluation of alterant geophysical tomography in welded tuff
Preliminary evaluation of alterant geophysical tomography in welded tuff