Numerical Study Investigating the Blasting Efficiency of the Long and Large-Diameter Uncharged Hole-Boring Method with Deck Charge Technique

The long and large-diameter uncharged hole-boring (LLB) method is a cut-blasting method used to reduce vibration induced by blasting. This method typically involves creating an uncharged hole with a 382 mm diameter and drilling 50 m in the tunnel excavation direction at a time. This method is reported to provide relatively good vibration reduction and with high blasting efficiency through short hole blasting compared to traditional cut methods. In this study, an advanced LLB method incorporating deck charge blasting was investigated to improve the blasting efficiency during long hole blasting. Numerical analysis was performed via ANSYS LS-DYNA to investigate the effectiveness of the deck charge technique. In the original LLB method, explosives were used to break the rocks more finely, and the fragmented rocks were concen trated at the end of the blast holes. On the contrary, the modified LLB, in which two-part explosives were loaded into the blast holes, is expected to push the fragmented rocks to the tunnel face more effectively than the original LLB method. Therefore, it is expected that the proposed LLB method combined with a deck charge technique can achieve superior blasting efficiency.