Post-test assessment of simulations for in situ heater tests in basalt—Part I. heater test description and rock mass properties

Abstract

Thermomechanical simulations were undertaken both a priori and a posteriori for two full-scale heater tests in shallow tunnels at the Near Surface Test Facility (NSTF) at Hanford, Washington. The Basaltic rock mass was investigated by an extensive laboratory and field programme involving geological characterization, core drilling and borehole testing, a field thermal test and a large-scale in situ flat jack test isolating 8 m 3 of columnar basalt. Rock mass thermal and mechanical properties were determined from these characterization data for input into thermomechanical simulations. The heater test systems are described along with the instrumentation, which consisted of numerous thermocouples, borehole extensometers, borehole deformation gauges and vibrating wire stressmeters. The determination of the rock mass thermal and mechanical properties from laboratory test data, geological characterization data and back-analysis of field property tests are detailed. The idealization of the basaltic rock mass was determined from interpretation of extensive geological characterization data; involving detailed field geologic mapping, borehole and core logging, rock mass classification schemes, impression packer tests, borehole geophysical tests, borehole jack deformation tests and laboratory and field experiments.