Verification of the bidirectional drilling and blasting method using TBM pilot tunnels

This paper deals with the possibility of the new drilling and blasting method which involves drilling of charge holes performed radially in advance on the wall of a pilot tunnel. Verification of the dynamic response between the existing method and the new one is performed to compare the relative decreasing effects of the vibration on the ground surface. Three dimensional dynamic analysis for the representative single blasting hole of the two blasting methods is Performed to compare the relative decreasing effects of the vibration on the ground surface. The results show that vibration due to the bidirectional drilling and blasting method is comparatively smaller than the vibration due to the existing blasting method at the surface of the ground directly above the tunnel. It is also analyzed that the dynamic response of the ground are influenced by the direction of the blasting holes. Therefore, it is concluded that the vibration can be reduced by controlling the direction of blasting holes according to the location of the ground structures which may be influenced.