Cycledrill and blast cycle

Drill and Blast Cycle
(Courtesy of Sandvik Tamrock Canada) This animated video demonstrates the steps involved in making a tunnel. The example shown is a large tunnel, such as one made to be used bycars or trains, but the tunnelling process is the same for mining underground. Step 1 Drilling and Surveying A jumbo is used to drill holes in the rock face. This one has three drilling arms and anoperator tower. It is run by electric cable; a hose brings water to the drills. The drills are pneumatic (new-mat-ic). That means that the drill bits both hammer and rotate. Broken bits of rock areflushed out by water. These drill holes are 2.4-3.6 metres long. The diagram in the lower right of the screen shows the location of holes drilled on the rock face, and the order in which they aredrilled. The first sets are straight holes (parallel cut) located around the edge of the face and in the middle. A second set (V-cut) is angled toward the center. These allow the rock to be blown away fromthe face into the drift (tunnel).

Step 2 Charging with Explosives Holes drilled are next filled with explosives. This is done by miners standing on the ground and, if the rock face is high, by usinganother jumbo with booms to lift the miner. Charging may be done using cartridge explosives, also known as stick powder or dynamite. The cartridges are placed in the holes and pushed to the backusing a wooden ramrod. A waterproof detonator cord, or fuse, hangs out of the end of each hole. The primer that starts the explosion is at the end of the fuse in the bottom of the hole. Charging may alsobe done using bulk explosives. This granular material, commonly ammonium nitrate fuel oil, is blown by air into the holes. Again the fuse with a primer at the far end hangs from each hole.

Step 3Blasting and Ventilation The individual fuses are connected to subfuses (yellow box) then to a main fuse (red box) in a way that ensure the holes are blasted in a proper sequence, from the center...