Rock mechanics instrumentation modifications for thermomechanical field tests in basalt at the Near-Surface Test Facility

In situ tests to characterize the thermomechanical behavior of basalt have been conducted at the Near-Surface Test Facility. Montoring of the rock mass response required the modification of existing geotechnical instrumentation. Additionally, characterization of the instrument response was necessary for the changing temperatures in field testing because of initial design for constant temperatures. The Basalt Waste Isolation Project (BWIP) has made an extensive effort to overcome the limitations of the existing monitoring instruments by modification and response characterizations for use beyond the range of their original design. This report summarizes the initial effort to improve the performance and response characterization of four basic geotechnical instruments used in monitoring the Full-Scale Heater Tests conducted at the Near-Surface Test Facility. These instruments are thermocouples, multiple-position borehole extensometers, borehole deformation gauges, and vibrating wire stressmeters. 16 refs., 37 figs., 1 tab.