Patent ID: 6532874
Filing Date: 2003-03-18
Classification: E21C,F42D

Abstract:
A blasting method of a bench of rock with two free surfaces consisting of an upper free surface and a slant free surface extended slantly from the upper free surface, which comprises the steps of:successively drilling a first group of first-order blasting holes consisting of two presplitting holes and one delay blasting hole positioned between the presplitting holes, a second-order blasting hole, and a second group of first-order blasting holes consisting of two presplitting holes and one delay blasting hole positioned between the presplitting holes, on the upper free surface of the bench of rock in a straight line, apart from the slant free surface at a desired distance, in which the first-order blasting holes of the respective groups are spaced apart from each other at a substantially equal interval, and the second-order blasting hole is spaced apart from the prespliting holes adjacent to the second-order blasting hole at a distance longer than the interval between the first-order blasting holes; charging the first- and second-order blasting holes with explosives, in which the delay blasting holes is charged in an indirect priming manner; blasting the first and second groups of first-order blasting holes, in such a manner that the presplitting holes are first blasted and then the delay blasting holes are blasted, so as to form four free surfaces around the second-order blasting hole; and blasting the second-order blasting holes where the four free surfaces were formed.