... against the stress ratio. As a result, it was confirmed that the stress-strain relation of the rock specimens were almost linear until the loading stage just before the failure and the elastic wave velocities of the rocks were not generally nearly decreased. Therefore, they has been shown it is reasonable...

... are probably due to conical, Hertzian cracks initiated at the surface of the rock specimens. Each of these load drops are corresponding to a material removal event in the region with positive hydrostatic stress (negative pressure) state at the rock surface enclosing the growing contact boundary. Moreover...