垂直変位を拘束した場合のせん断特性および異方性岩のせん断特性
岩の一面せん断試験に関する研究 (第2報)
1985 年 101 巻 1163 号 p. 1-7
詳細
1985 年 101 巻 1163 号 p. 1-7
Shear tests were conducted on sandstone and marble samples described in the lst. Report and on shale samples. Sandstone and marble were sheared while restricting normal displacement, and shale specimens sheared at constant normal stress perpendicular and parallel to stratification.
Normal stiffness values were higher for marble than sandstone. Shear stiffness increased with initial normal stress and indicated no glaring disparity between specimens sheared at constant normal stress and those sheared otherwise. Peak and residual strengths at corresponding normal stresses for both test procedures were virtually equal and the results compare favourably with those obtained by use of the triaxial compressive testing machine.
During shearing with restricted normal displacement, eventual maximum normal stresses were multiples of respective initial normal stresses. Gradients of positive slopes of curves for sandstone decreased as initial normal stress increased. Marble manifested a reverse trend. At failure, a conspicuous drop in normal stress was noticed for sandstone but marble exhibited no such phenomenon. These discrepancies are attributable to differences in their elastic module.
More powder was produced per unit shear displacement then during tests conducted at constant normal stress. Greding analyses of the powder indicate non-dependence of grain size on normal stress.
With shale, no significant difference was observed in seismic wave velocities measured perpendicular and parallel to stratification. Slightly lower peak but higher residual angles of internal friction and higher dilatancies were obtained for specimens sheared perpendicular to stratification.
Field and labolatory test results agree reasonably. Peak strengths of field tests fall between residual and peak strengths of laboratory tests.
