## 4 Analysis of Calculation Results
### Rock Crushing State Induced by Arcing-Blade Cutters
The crushing state inside the rock could be observed through a section cutting in the middle of the rock, where the cutter cut 200 mm, as shown in Figure 12. The variations in the crushing state with the cutter spacings under different penetrations are presented in Figure 13. When the penetration was 2 mm, the two crushed areas inside the rock were not connected and were independent of each other, which aligns with the observed phenomenon on the rock surface in Figure 9. On the other hand, under the 4 mm penetration condition, the two crushed areas inside the rock were connected with each other at cutter spacings of 40 mm and 50 mm, accompanied by the outward expansion of cracks, as exemplified in Figure 13(b1,b2). Similarly, the 6 mm penetration condition demonstrated analogous characteristics to the 4 mm penetration condition, with the two crushed areas being connected at the cutter spacings of 40 mm, 50 mm, and 60 mm, as depicted in Figure 13(c1-c3). Figure 11: Rock surface crushing state under 6 mm penetration with different cutter spacings: (a) 40 mm; (b) 50 mm; (c) 60 mm; (d) 70 mm; and (e) 80 mm. In order to visually understand the size characteristics of the crushed area, the crushed areas under different cutting parameters from Figure 13 are summarized in Figure 10.0 This reveals that the crushed area size was largest for penetration under 6 mm and smallest for penetration under 2 mm. Moreover, the crushing area size demonstrated an increasing trend with an increase in penetration. For instance, at a cutter spacing of 50 mm, as the penetration increased from 2 mm to 6 mm, the crushed area size escalated from 62.1 mm\({}^{2}\) to 1216.8 mm\({}^{2}\), leading to a nearly 19-fold increase. Notably, the crushing area size was also notably influenced by the cutter spacing when the penetration was consistent. At 2 mm penetration, the two cutters acted independently, resulting in similar crushing area sizes. At 4 mm penetration, the cutters exhibited a synergistic effect at cutter spacings of 40 mm and 50 mm, thereby crushing the rock ridge, leading to a substantial increase in the crushed area size from 340.8 mm\({}^{2}\) to 560.4 mm\({}^{2}\), an improvement of approximately 1.6 times. However, at a cutter spacing of 60 mm, the synergistic effect between the cutters diminished and the crushed area size decreased to 276.9 mm\({}^{2}\) and stayed stable at around 270 mm\({}^{2}\) with a further increase in the cutter spacing. When the penetration was 6 mm, the change trend in the crushed area was consistent with that of the 4 mm penetration, where the crushed area size substantially escalated from 480.1 mm\({}^{2}\) to 1550.7 mm\({}^{2}\) as the cutter spacing increased from 40 mm to 60 mm. When the cutter spacing was over 60 mm, the synergistic effect between two cutters disappeared, subsequent to which, the crushed area size rapidly decreased to 343.2 mm\({}^{2}\) and stabilized. Figure 10.1 Section position in the middle of rock sample. Figure 10.2 Crushing state of the cross-section at the middle position of the rock, P denotes penetration and S denotes cutter spacing. (**a1**) P = 2 mm, S = 40 mm; (**a2**) P = 2 mm, S = 50 mm; (**a3**) P = 2 mm, S = 60 mm; (**a4**) P = 2 mm, S = 70 mm; (**a5**) P = 2 mm, S = 80 mm. (**b1**) P = 4 mm, S = 40