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The drill cuttings from the reamer head fall to the floor of the lower level. The finished raise has smooth walls and may not require rock bolting or other forms of ground support. [ 1 ] One impressive use of raise boring is the 7.1 m diameter shafts for Sasol's Middelbult and Bosjesspruit Mines in South Africa.
There are three different classifications of drill bits used for drilling into stone: soft, medium, and hard. Soft formation rock bits are used in unconsolidated sands, clays, and soft limestones, etc. Medium formation bits are used in dolomites , limestones , and shale , while hard formation bits are used in hard shale, mudstones , granite ...
There are two principal phases of underground mining: development mining and production mining. Development mining is composed of excavation almost entirely in (non-valuable) waste rock in order to gain access to the orebody. There are six steps in development mining: remove previously blasted material (muck out round), scaling (removing any unstable slabs of rock hanging from the roof and ...