| Nonpenetrative crack will significantly weak the ability of compressive resistance of the soft rock and speed up the deformation velocity,so the quantitative study on the model of nonpenetrative fractured soft rock is very necessary.Using the uniaxial compression instrument and Particle Image Velocimetry technology,the specimens containing a pre-existing flaw with different inclination angle were produced by testing rock-like material,and a series of experiments were carried out to investigate the influence of the nonpenetrative crack on the mechanical properties of rock mass and crack coalescence process of soft rock.The experimental results show as follows.(1)When the initiation angle of the wing crack is between 0° and 45°,splitting failure is the main failure type,and the main crack is wing crack.When the initiation angle of the wing crack is between 45° and 90°,shearing failure is the main failure type,and the main crack is secondary crack.In this experiment,we found anti-wing crack mode only at α=60°,and it will occur cracking phenoomenon at the top of specimen under uniaxial compression.It can also observe wing crack inclination angle at α=15° 、 30° and 45°,and the wing crack inclination angle will decrease first then increase with the increase of the flaw inclination angle.The initiation angle of the wing crack is between 68° and 80° from the flaw plane.The wing crack inclination angle is minimum at α=30°.(2)The peak stress will decrease first then increase with the increase of the flaw inclination angle.Expecially when the flaw inclination angle is α=45°,the peak stress is 89% compared to complete specimen.The propagation of cracks will more easily happen when the inclination angle is larger.(3)From the cloud picture,the main displacement of the specimen mainly distribute in the left half of the slip plane consisted of the pre-existing flaw and the wing cracks,and slip down gradually with the increase of compression.The strain is mainly distribute in the slip plane,and the strain will increase with the increase of compression.Initial crack occur after the specimen has reached the peak stress.But the time interval is very short.The time interval is minimum at α=45° and maximum at α=75°.(4)Using the PIV technology can monitor the deformation and destruction of rock-soil mass,which has an effect on early-warning of mining security.Different with hard rock,soft rock has a low peak stress、fast destruction and long propagation after compression,so the time interval is very short compared to hard rock. |
