## 4 Analysis of Calculation Results
### Rock Crushing State Induced by Arcing-Blade Cutters  
At 2 mm penetration, the crushing states on the rock surface are depicted in Figure 9. The rock surface displayed two distinct \"strip\" crushed areas, which resulted from the successive cutting actions of cutter 1 and cutter 2. Notably, the cutters left undamaged rock ridges between the crushed areas. This observation aligns with the rock-breaking load law discussed in Section 4.1. Specifically, at a 2 mm penetration, there was a lack of synergistic effect between the cutters at any spacing. Therefore, the two cutters operated independently, leading to the formation of separate and non-interacting crushed areas. Furthermore, it was evident that these independent crushed areas did not affect each other. Additionally, with an increase in the cutter spacing, there was a corresponding increment in the width of the rock ridge. At a penetration of 4 mm, the crushing state of the rock surface is depicted in Figure 10. Figure 10a,b reveal an interconnected crushed area on the rock surface at cutter spacings of 40 mm and 50 mm, suggesting the crushing of the rock ridge by the two cutters. When the cutter spacing increased over 60 mm, the rock surface displayed two distinct crushed areas along with uncrushed rock ridges. Considering the analysis in Section 4.1, it can be concluded that, at the penetration of 4 mm, there existed a synergistic effect between the cutters under cutter spacings of 40 mm and 50 mm. This synergistic effect facilitated rock ridge crushing. However, with a further increase in cutter spacing, the synergistic effect weakened and may even have disappeared, leading to a failure in rock ridge crushing. Figure 9: _Cont._  
The crushing state on the rock surface when the penetration was 6 mm is illustrated in Figure 11. It is evident that a synergistic effect occurred between the two cutters when they were spaced at 40 mm, 50 mm, and 60 mm. Notably, in Figure 11a, the rock surface at the 40 mm position displays a strong synergistic effect, with the two adjacent crushed areas intersecting with each other and causing the intermediate rock ridge between two cutters to disappear. As the cutter spacing increased to 50 mm and 60 mm, as depicted in Figure 11b,c, the weakening of the synergistic effect between the cutters correlated with a gradual reduction in the level of rock ridge crushing. Moreover, as the cutter spacing increased, the weakening of the synergistic effect between the cutters correlated with a gradual reduction in the level of rock ridge crushing is also evident in Figure 11b. Figure 10: Rock surface crushing state under 4 mm penetration with different cutter spacings: (a) 40 mm; (b) 50 mm; (c) 60 mm; (d) 70 mm; and (e) 80 mm. Figure 9: Rock surface crushing state under 2 mm penetration with different cutter spacings: (a) 40 mm; (b) 50 mm; (c) 60 mm; (d) 70 mm; and (e) 80 mm. reached over 70 mm, as demonstrated in Figure 11d,e, the absence of the synergistic effect prompted the appearance of two distinct crushed areas and undamaged rock ridges on the rock surface. In summary, the degree of rock surface crushing was influenced by the penetration and cutter spacing. For instance, with a small penetration, such as 2 mm, there was an absence of synergy between two cutters at different cutter spacings in this paper. Under these cutting conditions, the two cutters acted independently to cut the rock, leading to a lack of interaction and inability to crush the rock surface. However, as the penetration increased to 4 mm and 6 mm, the synergistic effect between the cutters could effectively crush the rock surface given an appropriate cutter spacing. Notably, a smaller cutter spacing enhanced the synergistic effect and increased the degree of crushing.