Behaviour of rigid inclusion stressmeters in viscoelastic rock

Abstract The behaviour of the photoelastic glass-inclusion stressmeter was observed in specimens of rock salt under load. The meter maintained its calibration value (stress/fringe constant), both under conditions of constant load and under gradually increasing load, to within ±5% even though the rock material underwent appreciable creep deformation. When installed in a specimen of rock salt that was already under load the stressmeter was observed to pick up the absolute ambient stress in the host when observed over a period of time. Concurrently it responded immediately to an increase of stress generated in the host after the time of its insertion.