Experimental Study on Damage and Fracture Evolution Characteristics of Rock Material

The cement mortar specimens were used to simulate rock materials for uniaxial compression test and measurement of wave velocity during the test. Test results show that: The initial crack strengths of the specimens range from 7.41 to 8.89 MPa, with an average value of 8.32 MPa; the value of uniaxial compressive strength ranges from 13.44 to 14.93 MPa with an average value of 14.14 MPa. Overall view, the initial cracking strength of specimens fluctuates in a smaller range, but the uniaxial compressive strength is more discrete. The results of the wave velocity measurement show that: Before the surface of the specimen is cracked, the wave velocity of each measuring point has no obvious change with the increase of the load; when the specimen surface is cracked, the wave velocity of each the measured point decreased significantly with the increase of the load; after reaching the peak intensity, the wave velocity of each measuring point obviously decreased. From the obtained strain and wave velocity, the wave velocity and strain curve are plotted. The curve shows that each measurement point has a similar wave velocity-strain relationship diagram, the initial wave velocity values of measurement points 1#, 2#, and 3# are relatively close, and the initial wave velocity values of measurement points 5#, 6#, and 7# are relatively close to each other. The initial wave velocity value at 4# is in the middle of the initial wave velocity values at other measurement points, which is due to the uneven density distribution of the test piece.