Overcoring and calibration of IRAD GAGE stressmeters at the Spent Fuel Test in Climax granite

IRAD GAGE vibrating-wire stressmeters were installed in the Spent Fuel Facility at the Nevada Test Site to measure the change in in-situ stress during the Spent Fuel Test-Climax (SFT-C). Although extensive pre-installation laboratory tests were conducted, they were generic in nature. Unfortunately the degree of gage-rock contact has a strong influence on gage sensitivity and cannot be predicted before installation. This report discusses the results of removing a cylindrical section of rock and gages as a unit through overcoring and the subsequent post test calibrations of the stressmeters in the laboratory. With the assumption that the gage-rock contact was not disturbed by the overcoring, the results from these calibrations compensate for varying gage-rock contact. The estimated in-situ stresses based on post test calibration data are quite consistent with those directly measured in nearby holes. The magnitude of stress change calculated from pre-installation test data is generally much smaller than that estimated from post test calibration data