Core disking and its relationship with stress magnitude for Lac du Bonnet granite

Abstract

Core disking is an indicator of elevated stress magnitudes. Disked cores from boreholes drilled from underground excavations in massive unfractured granite, 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 for three disk thickness categories; (1) thin ( t / D < 0.2 ) , (2) medium ( 0.2 < t / D < 0.4 ) and (3) thick ( 0.4 < t / D < 2.2 ) and partial disking. The data suggests that core disking initiates when the maximum principal stress normalized to the tensile strength is 6.5.