NON-ELECTRIC DELAY BLASTING

A non-electric delay blasting method is provided which comprises the use of single trunk line of detonating cord having a series of detonating relays, all of the same delay period, connected at spaced intervals along its length. Branch lines of detonating cord are connected in groups to the trunk line in the intervals between the relays and each branch line has a delay detonator of the same delay period attached thereto. The delay period of the relays is shorter than that of the delay detonators. The detonators within the groups detonate in a random manner. The method eliminates the need to use large numbers of different delay period detonators in a multi-charge blast thus simplifying preparation of the charge and reducing inventories.