## 5 Numerical Simulation of Blasting Hole Network Parameters
### Numerical Simulation Results
After determining the propagation law of stress wave and rock failure under different working conditions, in order to further illustrate the stress change between two cylindrical blast holes and optimize the parameters of a pre-splitting blasting hole network reasonably, the effective stress peaks of each observation point of the above 30 groups of models are extracted and fitted. The fitting results are shown in Figure 16a-e. It can be seen from the following figure that the effective tensile stress decreases with the increase in the hole spacing, indicating that after the explosion begins to act on the rock mass, under the same other conditions, the hole spacing is inversely proportional to the effective stress, and the form of the wave gradually decays from the shock wave to the compression wave and finally becomes a seismic wave. For a small aperture (90-100 mm), with the increase in the hole spacing, the attenuation rate of the effective tensile stress decreases gradually, indicating that the explosive gas and the stress wave consume a lot of energy in the formation of the plastic flow zone of the two holes, and the effective tensile stress shows a continuous attenuation trend due to no energy supplement in the later stage. For large apertures (110-130 mm), the attenuation rate of effective tensile stress gradually increases with the increase in aperture spacing. It is considered that it may be caused by the larger loading amount of the large aperture than that of the small aperture. With the increase in loading amount, the corresponding stress wave energy and the generated explosive gas also increase. Figure 15: Y-direction peak stress curve at observation point. (**a**) 90 mm aperture. (**b**) 100 mm aperture. (**c**) 110 mm aperture. (**d**) 120 mm aperture. (**e**) 130 mm aperture. The obtained fitting data were screened to obtain the corresponding optimal pore spacing multiple relationship under each hole diameter; that is, the effective tensile stress of rock just reaches the ultimate dynamic tensile strength of rock, and the optimal hole diameter and pore spacing combination of rock mass will not be excessively damaged. The optimal fitting curve is shown in Figure 17. Figure 17 shows that the hole spacing is proportional to the hole diameter, and it increases with the increase in the hole diameter. The fitting coefficient is greater than 0.93, and the following expression is obtained:  
\[\text{y}=1.12+0.076\text{x} \tag{11}\]  
Formula: y--Optimal hole diameter and distance between holes. x--hole diameter. At present, the formula is suitable for rock Pu's hardness \(f\) = 8-14; the explosive detonation velocity is about 3500 m/s, and the use of uncoupled charge reverses the initiation of open-pit pre-splitting blasting engineering. The formula can calculate and analyze the optimal hole spacing corresponding to different apertures in order to ensure the half hole rate and flatness after blasting and prevent excessive damage to rock mass, providing certain reference values for future pre-splitting blasting engineering. Figure 16: The relation curve between effective tensile stress of different hole diameters and hole spacing. (**a**) 90 mm aperture. (**b**) 100 mm aperture. (**c**) 110 mm aperture. (**d**) 120 mm aperture. (**e**) 130 mm aperture. Figure 17: Optimization curve.