In-situ Stress Magnitude and Core Disking

Accurate measurement of in situ stress using surface-drilled deep boreholes is a challenge in high stress regimes in which both horizontal stresses exceed the vertical stress. For such stress regimes core damage and core disking is often observed and these observations were used to constrain the stress state.;Disked cores from boreholes drilled from underground excavations in massive unfractured granite at AECL0s Underground Research Laboratory, where the stress magnitudes are known with confidence, were used to establish a relationship between core disk thickness and the stress magnitude. Relationships were established three disk thickness categories; (1) thin (t/D<0.2), (2) medium (0.2