Shear Tests under Constant Deformation Rate and Shear Properties of Rocks by Use of a Newly Designed Direct Shear Testing Machine

With the aim of carrying out direct shear tests under high normal stress on intact rocks and rocks containing discontinuity planes, we designed a new direct shear testing machine which was used in the present investigation.Two types of rock, Ainoura sandstone and Akiyoshi marble, were used in our tests. Obtained data give very plausible shear stress versus shear displacement curves which are comparable with those of triaxial tests.A strength drop is noticed in the saturated state as is the case with triaxial tests. It is also observed that data on the failure criterion are very reproducible but have slightly higher peak and slightly lower residual values than those from triaxial tests.Particular attention is drawn to the interesting fact that rock dilatancy characteristics can be observed during shear.