Rate-dependent mechanical characteristics of rock-like specimens containing single closed crack

Uniaxial compression test was carried out to study the combined effects of inclination angle of prefabricated closed crack and strain rate on the mechanical properties and fracturing behaviors of fissured rock. The experimental results demonstrate that strain rate and inclination angle of closed crack alpha significantly affect the mechanical properties and fracturing behaviors of fissured specimens. Under the combined effect of strain rate and inclination angle, the shear dominant failure pattern was the main failure pattern for the specimens with prefabricated closed crack alpha = 60 degrees while the tensile dominant failure pattern was the main fracturing patterns for others. When alpha was invariant, the peak strength, strain at peak stress and post-peak softening modulus rose with the increase of the strain rates; on the contrary, the residual compressive strength decreased with the increase of the strain rates. Under the same strain rate, the peak strength first decreased and then increased. Besides, the strain at peak stress firstly increased and then decreased with the increase of alpha. The post-peak softening modulus increased before the crack inclination angle alpha reached to 45 degrees, and then decreased. Meanwhile, the change law of residual compressive stress with the increase of inclination angle of closed crack was increase-decrease-increase. Under the same strain rate, the initiation angle at the loading end of the prefabricated closed crack first decreased and then increased, while the initiation angle theta(1) at the bearing end decreased with the increase of alpha. When alpha was constant, the initiation angle at the loading end decreased before alpha reached to 60 degrees with the increase of strain rate, and then increased when alpha = 90 degrees. Meanwhile, the initiation angle at the bearing end decreased with the increase of strain rate. Under the same strain rate and the same inclination angle, due to unidirectional loading, the initiation angle at bearing end was relative smaller than the initiation angle at the loading end and the crack initiation at the loading end of the prefabricated crack was earlier than that at the bearing end.