| Popis: |
Chemical methods involve the use of explosives or expanding gas cartridges, use of the latter being uncommon. The most common method is to place explosives in boreholes drilled vertically into the material to be blasted. A grid of boreholes is drilled, coveting the area to be pre-treated. Loading and firing of the charges is carried out in convenient groups of boreholes. The work is usually carried out from a floating or self-elevating pontoon but is occasionally carried out underwater by divers with submersible drills. High explosives are also used underwater in the form of surface, or lay-on, charges. These charges are laid on the surface of the material to be broken up and are used in three forms; cartridges, slabs, or shaped charges. The standard method of breaking rock mechanically, and one which has been around for at least the last century, is the simple rock breaker, consisting of a pontoon on which is mounted one or more heavy needles or chisels. This device, which could be formed from a heavy pile with a suitably hardened tip, is hoisted and dropped vertically on the material to be broken. Fragmentation is caused by shearing or crushing the rock, depending on its formation and crystalline structure. |
