Abstract:

Bedrock intruding into the tunneling scope is a problem frequently encountered in shield tunneling. In the object project, the bedrock intruding into the tunneling scope is pretreated by means of blasting hole drilling from the ground surface and blasting underground. For bedrocks with different thicknesses, different blasting hole spacing and different charging quantities are adopted. After blasting, highdensity electricity method and core drilling method are adopted to verify the blasting effect. The results show that the fragmentation of the bedrocks has achieved good effect: the maximum length of the cores measured is 42 cm and the length of 97.4% of the cores is less than 30 cm. The practice demonstrates that the pretreatment of the bedrocks by means of blasting hole drilling from the ground surface and blasting underground is feasible and the requirement of successful shielding tunnel can be met. 

Key words: shield tunneling, bedrock intrusion, blasting hole drilled from ground surface, highdensity electricity method, core drilling method