Comparison study on rock crack pattern under a single normal and inclined disc cutter by linear cutting experiments

In order to study the crack pattern of Beishan granite under a single normal and inclined disc cutter, a series of linear cutting experiments were conducted. During the tests, a constant cross-section disc cutter with a diameter of 17 in. was used and a block of Beishan granite with the size of 1000 × 1000 × 600 mm (Length × Width × Height) was adopted. After the experiments, it is found that in the rock sample, there is a broken area beneath the cutting groove with variable degrees of fragmentation. Based on the crack pattern and crack density, the rock sample is divided into the re-compacted zone, the crushed and crack zone, and the intact rock zone. Meanwhile, the size and area of these zones were analyzed and the corresponding ultrasonic velocities were measured. It is shown that the crack patterns for normal and inclined cuttings at the same penetration depth are greatly different due to different included angles and cutting forces in the two scenarios. As the penetration of inclined cutting increases, the size and area of various zones expand significantly. In addition, the ultrasonic test reveals that the ultrasonic velocity of each zone agrees well with the degree of fragmentation and the velocities of corresponding zones for different scenarios are similar.