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Observations of water movement in a block of fractured welded Tuff

Conference ·
OSTI ID:113825
;  [1];  [2];  [3]
  1. Geological Survey, Denver, CO (United States)
  2. Foothills Engineering Consultants Inc., Golden, CO (United States)
  3. ROCKTECH West Jordan, UT (United States)
A laboratory water infiltration experiment through a block of fractured, moderately welded volcanic tuff was conducted at different boundary pressures. The block measured 47.5 cm long {times} 54.3 cm wide {times} 80.6 cm high. The purpose of the experiment was: (a) to test an instrumentation scheme for a field test, and (b) to make flow measurements through a fractured network at different boundary pressures to understand mechanisms that affect fracture flow. The upper boundary water pressure was decreased in steps; each step lasted several weeks where the pressure was kept steady. Water inflow and outflow rates were measured for each boundary condition. Entrapped air was found to impede water movement. The gas phase in the fracture network was found to not be continuous; its pressure within the network was not known. The matric potential values could not be measured with tensiometers alone since a known gas pressure is required. Long-term input and output flow rates were equal. Outflow rate did not stabilize during the test period; it continued to decrease, even when the upper boundary water pressure was kept steady. No relation between boundary pressure and flow rate was established. Bacteria, which was found in the outflow, possibly caused variations in the behavior. Trapped air caused the outflow to periodically decrease or stop; however, outflow rates following the interruptions did not change long-term flow trends.
Research Organization:
Geological Survey, Denver, CO (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States)
DOE Contract Number:
AI08-92NV10874
OSTI ID:
113825
Report Number(s):
CONF-940553--86; ON: DE96001452
Country of Publication:
United States
Language:
English