A 42mm-diameter intact rock specimen fails in a uniaxial compression test at an axial load of 20 kN. The rock behaves according to the Mohr-Coulomb criterion, with an angle of friction 38 degrees found in the triaxial tests. A specimen of diameter 42mm would fail in a triaxial test with the confining pressure of 10MPa. The values of ??and m in the Hoek-Brown criterion that would give the same failure loads as the Mohr-Coulomb criterion, for the uniaxial and triaxial tests referred to above is respectively ?? 75.14MPa and m 7.76. Calculate by how many percent the Hoek-Brown criterion with ??and m as determined in (c) overestimates or underestimates the axial load at failure compared to Mohr-Coulomb criterion, when the confining pressure is 10MPa and when it is 20MPa
A 42mm-diameter intact rock specimen fails in a uniaxial compression test at an axial load of 20 kN. The rock behaves according to the Mohr-Coulomb criterion, with an angle of friction 38 degrees found in the triaxial tests. A specimen of diameter 42mm would fail in a triaxial test with the confining pressure of 10MPa. The values of ??and m in the Hoek-Brown criterion that would give the same failure loads as the Mohr-Coulomb criterion, for the uniaxial and triaxial tests referred to above is respectively ?? 75.14MPa and m 7.76.
Calculate by how many percent the Hoek-Brown criterion with ??and m as determined in (c) overestimates or underestimates the axial load at failure compared to Mohr-Coulomb criterion, when the confining pressure is 10MPa and when it is 20MPa.
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