Abstract: The present invention relates to a method for forming a parallel bore hole and a slant bore hole (or V-shaped V bore hole) together within the same area of a working face, and then blasting the working face by using a delay electric detonator. The method of this invention includes the steps of drilling a number of V holes at a predetermined angle in a horizontal angle cut pattern or in a vertical angle cut pattern about the central zone of a working face, drilling a number of parallel cut hole within a projective area of the above mentioned slant holes; loading an electric detonator in the slant holes and an explosive material by indirect priming in the parallel cut holes up to the bottom of the slant holes; blasting the slant holes to form a slant free surface; blasting a center cut hole out of the parallel cut holes to form two free surfaces having a funnel shape; and sequentially blasting a middle cut hole and an outer cut hole out of the parallel cut holes to form a cubical space.
Type:
Grant
Filed:
July 11, 1996
Date of Patent:
June 3, 1997
Assignee:
Sungkyong Engineering & Construction Limited