Do Empty holes affect damage depths of rock mass under multi-long-hole blasting?

The significant actions of depths of empty holes on the damage depths of rock mass under the multi-long-hole blasting is due to the fact that the blast-induced rock deformation in main blasting areas is greatly affected by the presence of empty holes.

Are empty holes more severe than without empty holes?

Moreover, it can be seen that the rock damage near the ground surface in the case with empty holes is obviously more severe than that without empty holes due to the combined reflection actions of empty holes and ground surface on blast-induced stress waves. Final damage of rock mass under multi-long-hole blasting with and without empty holes

How do empty holes affect rock damage?

The empty holes significantly affect the generation, connection, and aggregation of rock damage under blast loads. Damage modes of rock mass at different time instants under multi-long-hole blasting with large empty holes. Deformations in partial figures is enlarged to five times for illustration

Do Empty holes increase rock deformation?

In addition, it can be found that the rock deformation near the empty holes along the connection of the centric main blasting borehole and empty holes in the B–B section is obviously increased in the case with 250 mm diameter of empty holes, while it is not significantly increased in the cases with 200 mm and 150 mm diameters of empty holes.

Does depth of empty holes affect size distribution of rock fragments?

The results indicate that increasing the depth of empty holes beyond a certain level (e.g., 7 m in this study) can generate more small sizes of rock fragments under the multi-long-hole blasting with empty holes. Size distributions of blast-induced rock fragments in the cases with different depths of empty holes.

What happens when a drill bit hits a rock?

Due to the continuous interplay between drilling speed and rotational speed during the drilling process, significant impact pressure and torque are generated shortly after the drill bit initially contacts the rock. At this point, drilling is in an unstable state.