Laboratory study of fracture healing in Topopah Spring tuff: Implications for near field hydrology
Seven Topopah Spring tuff samples were studied to determine water permeability in this rock under pressure and temperature conditions similar to those expected in the near field of a nuclear waste package. Six of the seven samples were studied under isothermal condition; the other was subjected to a thermal gradient. Four of the six fractured samples contained a reopened, healed, natural fracture; one contained an induced tensile fracture and the other contained a saw-cut. The fracture surfaces were examined using scanning electron microscope (SEM) before and after the experiments and the water that flowed through the samples was sampled for chemical analysis. The experimental durations ranged from about 3 months to almost 6 months. Water permeability of the fractured samples was found to decrease by more than three orders of magnitude when the sample temperature increased to 150{degree}C. The sharpest decrease in permeability occurred when the temperature was increased above 90{degree}C. Permeability of the intact sample did not change significantly under the similar experimental conditions. When the temperature returned to room conditions, the water permeability did not recover. The mechanical strength of one healed sample was about half that of the intact rock. SEM studies of the fracture surfaces and water chemical analysis of the water suggested that both dissolution and deposition occurred on the fracture surfaces. Smoothing of fracture asperities because of dissolution and deposition was probably the main cause of the permeability decrease. Deposition of dissolved silica was probably the main cause of fracture healing. 12 refs., 6 figs., 1 tab.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 137610
- Report Number(s):
- UCRL-100624; CONF-890928-18; ON: DE90005325; TRN: 90:004449
- Resource Relation:
- Conference: Nuclear waste isolation in the unsaturated zone: FOCUS `89, Las Vegas, NV (United States), 18-21 Sep 1989; Other Information: PBD: Sep 1989
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC FRACTURES
REPAIR
TUFF
PERMEABILITY
HIGH-LEVEL RADIOACTIVE WASTES
UNDERGROUND DISPOSAL
TEMPERATURE EFFECTS
SILICON OXIDES
DEPOSITION
HYDROLOGY
FIELD TESTS
YUCCA MOUNTAIN
ISOTHERMAL PROCESSES
TEMPERATURE GRADIENTS
PRESSURE EFFECTS
SURFACES
DISSOLUTION
EXPERIMENTAL DATA
EVALUATED DATA
BENCH-SCALE EXPERIMENTS
SCANNING ELECTRON MICROSCOPY
PRECIPITATION
SITE CHARACTERIZATION
Yucca Mountain Project