## 6 Discussion  
By calibrating the material parameters of the rock, the simulation results were matched with the uniaxial compression test. On this basis, a simulation model for cutting red sandstone with an arcing-blade cutter was established. Based on the above analysis, the rock-breaking load of the arcing-blade cutter exhibited fluctuation characteristics when cutting rock. The three-directional loads obtained from the simulations were compared with the maximum vertical force, followed by the rolling force and the minimum lateral force. At a penetration of 2 mm, the rock-breaking load of the arcing-blade cutter did not change with an increase in the cutter spacing. At penetrations of 4 mm and 6 mm, as the cutter spacing increased, the vertical force and rolling force showed a trend of first  
Figure 18: Specific energy in experiments.  
Figure 17: Crushing state of rock surface in experiments: (**a**) 2 mm penetration and (**b**) 4 mm penetration. (**a**) P = 2 mm, S = 40 mm; (**a**2) P = 2 mm, S = 50 mm; (**a**3) P = 2 mm, S = 60 mm; (**a**4) P = 2 mm, S = 70 mm. (**b**1) P = 4 mm, S = 40 mm; (**b**2) P = 4 mm, S = 50 mm; (**b**3) P = 4 mm, S = 60 mm; (**b**4) P = 4 mm, S = 70 mm.  
increasing and then maintaining stability, while the trend of the lateral force change was the opposite, showing a first decreasing trend and then maintaining stability around 0. The above explanation shows that there was a synergistic effect between the two arcing-blade cutters under the conditions of penetrations of 4 mm and 6 mm. The synergistic effect can promote rock crushing. However, this synergistic effect between the arcing-blade cutters will weaken or even disappear with an increase in cutter spacing. In addition, under the condition of a penetration of 2 mm, there was no synergistic effect between the two arcing-blade cutters, so the rock-breaking load did not change significantly.  
The rock crushing state was closely related to the rock-breaking load. At a penetration of 2 mm, due to the inability of the arcing-blade cutters to synergistically break the rock, unbreakable rock ridges appeared at different cutter spacings in this paper. The crushed area generated by the two arcing blade cutters could not be effectively connected. Under the 4 mm and 6 mm penetrations, there existed a limit on the cutter spacing value, which connected the crushing area generated by the two arcing-blade cutters. The rock ridge was completely crushed. As the cutter spacing further increased beyond the limit value, the rock ridge could not be broken. The cutter spacing limit values at the 4 mm and 6 mm penetrations were about 50 mm and 60 mm, respectively.  
In addition, the crushing efficiency of the arcing-blade cutter was related to the crushing state of the rock. At a penetration rate of 2 mm, the two arcing-blade cutters were unable to synergistically break the rock, resulting in a stable specific energy at any cutter spacing. However, at penetration rates of 4 mm and 6 mm, the specific energy showed a trend of first decreasing, then increasing, and finally maintaining stability as the cutter spacing increased. This indicates that the arcing-blade cutter had the highest crushing efficiency at the cutter spacings of 50 mm and 60 mm under the penetration rates of 4 mm and 6 mm. Interestingly, the experimental results from the liner cutting of the arcing-blade cutter also confirmed this conclusion. It shows that the simulations are reliable.