B. Haimson et al., ESTIMATING THE STATE OF STRESS FROM SUBHORIZONTAL HYDRAULIC FRACTURESAT THE UNDERGROUND RESEARCH LABORATORY, MANITOBA, International journal of rock mechanics and mining sciences & geomechanics abstracts, 30(7), 1993, pp. 959-964
We conducted 9 complete hydraulic fracturing in situ stress measuremen
ts in vertical borehole HF1 at the 420 Level of AECL's Underground Res
earch Laboratory (UPL), near Pinawa, Manitoba. The tests did not resul
t in vertical fractures. Thus, a generalized least-squares criterion w
as employed to compute the estimated principal horizontal in situ stre
sses. The large number of redundant test results enabled us to estimat
e the stress condition with confidence, even though the hydraulic frac
tures were only gently inclined. The estimated in situ stress regime w
ithin the range between 25 and 95 m below the 420 Level (445-515 m bel
ow the surface) is S(v) = 12-14 MPa; S(h) = 36(+/-16) MPa; S(H) = 54(/-13) MPa at 120-degrees(+/-32-degrees). The results are consistent wi
th other independently conducted measurements at the URL.