A study on hole-cutting in deep tunneling

This study is to investigate the hole cutting in deep tunnels. The study background is firstly briefed. UDEC is then used to simulate the hole cutting process at various cases. The modeling result indicates that the two-stage hole cutting is more efficient than the full length hole-cutting and the mechanism could be that the first half hole-cutting can provide additional free face for the second half hole-cutting in the two-stage hole cutting. It is shown that the empty holes play a very important role in the straight hole cutting to increase the blast efficiency. The reason is that the empty holes provide more free face and rock a greater deformation. The modeling result is then used to optimize the rock blasting design.