Patent ID: 6454359
Filing Date: 2002-09-24
Classification: E21D,F42D

Abstract:
A tunnel blasting method, comprising:drilling blast holes including cut holes, cut spreader holes, floor holes and roof holes to predetermined depths and in a predetermined hole arrangement, loading said blast holes with one or more detonators and explosives, stemming said blast holes with stemming materials, and detonating said detonators using a triggering device, wherein said loading step comprises: mounting one or more air bladders in each of said blast holes to form an air decking of a predetermined size so that a front free surface or one or more small free surfaces are formed, the air decking being adapted for enlarging a projective area toward said front free surface or one or more small free surfaces and increasing a total blast pressure so as to increase the fragmentation rate of rock and reduce blast vibration; and changing the lengths of said one or more air bladders according to the diameter variations of said blast holes upon the blasting operation, while maintaining the lengths of the stemming materials at least substantially constant among said blast holes.