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Unformatted text preview: This may be mentioned that use of stoper or parallel raise
feed drills is made while driving all types of raise except those driven by the use of
blasthole drills and raise borers. In these raises use of conventional explosives is also
made to blast them. © 2005 by Taylor & Francis Group, LLC 334 SURFACE AND UNDERGROUND EXCAVATIONS Raising techniques Without aid of explosives With aid of explosives Conventional Open
raising Using climbers Compartment Jora
hoist Blasthole techniques Alimak raise Longhole Drop
raising raising Raise borers Drilling up Drilling down
reaming down reaming up Pneumatic Electrical Diesel Figure 13.3 Classification of vertical/steeply inclined raise driving techniques based on the
rock fragmentation mechanism. 13.5 CONVENTIONAL RAISING METHOD: OPEN RAISING
This is the oldest and simplest method of driving raises of very short length particularly in the competent ground. The process consists of drilling and blasting the initial
2–3 rounds of 1.5 to 2 m, using the blasted muck to stand on. But after this stulls or
stage bars are used to prepare a stage (platform), as shown in figure 13.4(a). This stage
is used to carry out drilling and blasting operations. Before blasting any round; holes
are drilled for the next platform, fixing a pulley (sheave) block, and to hang a rope ladder. The pulley block is used for supplying material at the face and the rope ladder for
accessing the face. Before blasting a round the planks from the working stage are
removed, and only the stulls are kept in place. Thus, the operation is not without risk
and difficulties. This, in turn, limits application of this method for driving raises usually not exceeding 10 m.
13.6 CONVENTIONAL RAISING METHOD: RAISING BY
This technique is an improvement over the open raising method. The method involves
dividing the raise into two compartments, as shown in figure 13.4(b). One of the compartments, known as man-way compartment, is used to install service lines such as
water, compressed air, ventilation ducts, pulley block for material hoisting and the ladders. The other one is used to accommodate the blasted muck. The parting is built by
fixing the wooden logs/sleepers skin to skin. After every blast the muck is drawn from
the bottom so that its level is maintained at the same height as that of the man-way
compartment. Before blasting any round the man-way compartment is covered using
an inclined bulkhead to divert the blast’s fragments towards the muck compartment
and thereby avoiding any damage to its fittings. However, while re-approaching the
face after blasting due precaution is necessary. The method is slow and tedious but
allows raises of longer lengths than the open raising method. In place of two compartments it could be equipped with three compartments to drive raises of large crosssection. Open raising and this method are practically useful for small mines with low © 2005 by Taylor & Francis Group, LLC EXCAVATIONS IN UPWARD DIRECTION – RAISING 335 2...
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This document was uploaded on 02/12/2014.
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