HUGE BLASTING OPERATION

Southland Times, Issue 24773, 18 June 1942, Page 4

HUGE BLASTING OPERATION

LIMESTONE ROCK DISPLACED Two and a-half tons of gelignite were used yesterday in the largest single blasting operation ever undertaken in Southland. This huge quantity of explosives displaced about 40,000 cubic yards of limestone on the quarry face of the Browns lime works, and the loosened rock will probably be sufficient to supply the works with raw material for more than six months. As a producer of noise, the explosion was disappointing and at what most of the spectators considered a safe distance the blast was a dull roar accompanied by only a slight ground tremor. The gelignite had been planted so deeply in the rock that no eruption skywards of loose stones occurred. From about 3000 to 5000 cubic yards of limestone fell into the quarry and probably made more noise than the subterranean explosion of the gelignite. TUNNEL IN LIMESTONE

At the foot of a face of limestone 60 feet high a tunnel four feet wide and six feet high’had been driven for a distance of 57 feet. At the end of the main drive two smaller tunnels were cut at right-angles in opposite directions for nearly 30 feet. At the far end of each about 40 cases of gelignite were laid and the tunnels then sealed with about 18 feet thicknesses of concrete. About 30 feet from the face two more short tunnels were driven at right angles to the main shaft for a distance of 20 feet and about 10 cases of explo* sives sealed in thick concrete. Altogether, 50001 b of gelignite costing £7OO were used in the operation. The charge was fired electrically from the head of the conveyor belt about 100 yards away. The man who fired the charge felt a severe earth jolt, but the fears of spectators that the blast might be felt a considerable distance away were not realized. The limestone was shattered for a distance of 75 feet back from the face. It should be possible to pick up this material with a steam shovel without the use of more explosives. Efforts are being made to increase the output of the works substantially. In the past it has produced from 25,000 to 30,000 tons of lime a year, and it is hoped that this total will be almost doubled.