Cd. Martin et B. Stimpson, THE EFFECT OF SAMPLE DISTURBANCE ON LABORATORY PROPERTIES OF LAC DU BONNET GRANITE, Canadian geotechnical journal, 31(5), 1994, pp. 692-702
Laboratory properties of Lac du Bonnet granite samples collected at de
pths ranging from near-surface to 1000 m were established. The laborat
ory properties indicated that either the in situ properties were chang
ing with depth or the samples were changing with depth. Comparison of
P-wave velocities in the samples and in situ confirmed the latter, i.e
., sample disturbance was affecting the laboratory properties. The str
ength of the damaged samples indicated that sample disturbance affecte
d the cohesion of the material, not the frictional properties, and tha
t the cohesion loss cannot be accounted for, by applying a confining s
tress. Sample disturbance started to affect the laboratory properties
of Lac du Bonnet granite when the maximum far-field in situ stress exc
eeded about 10% of the unconfined compression strength.