# Double-Borehole Superimposed Effect of a New Non-Explosive Directional Rock-Breaking Method
## 3 Results
### Numerical Simulation Results of IESF
#### 3.1.2 Strain Field Evolution Law for Double-Hole Fracture  
The strain evolution processes during fracturing by CB, SCB, and IESF are respectively illustrated in Figures 18-20. In CB, the first 50 steps (Steps 0-50) exhibited substantial strain in all directions around both boreholes due to omnidirectional stress wave extension, while during the subsequent 50 steps (Steps 50-100), high strain concentrations remained within a confined area near the boreholes, with only the four main fractures originating from the left borehole and the five main fractures from the right borehole showing significant strain beyond this zone, and strain in other regions diminishes considerably. In SCB, significant strain was observed in all directions within a limited radial range around both boreholes, while beyond this critical distance, elevated strain concentrations were localized exclusively along the slotted orientations, demonstrating superior directional rock-breaking efficacy compared to CB. Additionally, the strain reduction was observed at the fracture tips of the two directional fractures. During rock fragmentation using IESF, elevated strain concentrations were localized exclusively along the slotted orientation of both boreholes, while minimal strain was observed in all other directions. It demonstrated the optimal directional fracture control capability of IESF. Figure 18: The strain evolution in CB. At Step 80, a concentric circle with a radius of 0.135 m was selected around the right slotted borehole. Strain values at 0\({}^{\circ}\), 30\({}^{\circ}\), 60\({}^{\circ}\), 90\({}^{\circ}\), 120\({}^{\circ}\), 150\({}^{\circ}\), 180\({}^{\circ}\), 210\({}^{\circ}\), 240\({}^{\circ}\), 270\({}^{\circ}\), 300\({}^{\circ}\), and 330\({}^{\circ}\) positions along this circle were recorded for CB, SCB, and IESF. For CB, strain  
Figure 19: The strain evolution in SCB. Figure 20: The strain evolution in IESF. values were additionally recorded at the intersections of this circle with the five primary fractures, located at angles of 38\({}^{\circ}\), 86\({}^{\circ}\), 127\({}^{\circ}\), 192\({}^{\circ}\), and 330\({}^{\circ}\) (these points were included in the aforementioned angular positions). The strain distributions at characteristic points along the circle for all three fracturing methods are illustrated in Figures 21-23. In CB, significantly higher strain concentrations were observed at the intersections of the five primary fractures (38\({}^{\circ}\), 86\({}^{\circ}\), 127\({}^{\circ}\), 192\({}^{\circ}\), and 330\({}^{\circ}\)) with the concentric circle, recording strain magnitudes of 7 mm, 6 mm, 6 mm, 9 mm, and 8 mm, respectively. In contrast, the remaining points along the circle exhibited minimal strain values ranging from 1 mm to 2 mm. In SCB, significantly higher strain concentrations were localized along the energy-focused directions (0\({}^{\circ}\) and 180\({}^{\circ}\)) on the circle, with strain magnitudes of 7 mm and 8 mm, respectively. Perpendicular to the energy-focused directions (90\({}^{\circ}\) and 270\({}^{\circ}\)), strain values were reduced to 1.5 mm, while all other non-shaped charge directions exhibited strain below 1.5 mm, demonstrating that SCB effectively achieved directional rock fragmentation. During rock fragmentation using IESF, strain magnitudes of 6 mm were concentrated along the slotted orientations (0\({}^{\circ}\) and 180\({}^{\circ}\)), while non-slotted directions (30\({}^{\circ}\), 60\({}^{\circ}\), 90\({}^{\circ}\), 120\({}^{\circ}\), 150\({}^{\circ}\), 210\({}^{\circ}\), 240\({}^{\circ}\), 270\({}^{\circ}\), 300\({}^{\circ}\), and 330\({}^{\circ}\)) exhibited uniformly low strains of 1 mm. Both IESF and SCB produced much larger strain in the energy-focused directions than in the other direction, and both maintained lower strain levels in the non-energy-focused direction. However, the IESF did not show the phenomenon of strain prominence perpendicular to the energy-focused directions like SCB.