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Heated flatjack test series to measure the thermomechanical and transport properties of in situ rock masses (heated block test)

Technical Report ·
OSTI ID:6700783

An instrumented 8 m/sup 3/ block of jointed gneiss was subjected to biaxial and uniaxial loading at ambient and elevated temperatures, using flatjacks and a line of borehole heaters. The following rock mass properties were investigated under various conditions of stress (0 to 6.9 MPa, uniaxial and biaxial) and temperature (12 to 74/sup 0/C mean block temperature): joint permeability, static modulus, dynamic modulus, joint normal and shear stiffness, coefficient of thermal expansion, thermal conductivity and diffusivity. The instrumentation array included multiple position borehole extensometers, DCDT and IRAD surface strainmeters, various borehole stressmeters and deformation gages, numerous thermocouples and Whittemore strain gage measurement points. The coefficient of thermal expansion was found to initially reduce with increasing temperature in the horizontal loaded directions, and to increase in the unloaded vertical direction. Static moduli varied with gage length and with the location of each instrument relative to jointing, yielding a distribution of moduli and Poisson's ratios. Joint permeability reduced by a factor of four under ambient loading (0 to 6.9 MPa), and by a factor of thirty when coupled with a 60/sup 0/C rise in rock temperature, at unchanged stress.

Research Organization:
Terra Tek, Inc., Salt Lake City, UT (USA)
DOE Contract Number:
AC06-76RL01830
OSTI ID:
6700783
Report Number(s):
ONWI-260; ON: DE83000728
Country of Publication:
United States
Language:
English