5 m 09 m 16 m 12 m 3 2m 4 5 18 m 2 1 23 m 23 m 1 2

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Unformatted text preview: .5 m 0.9 m 1.6 m 1.2 m 3 2m 4 5 1.8 m 2 1 2.3 m 2.3 m 1 2 Section Section (b) Raising by compartment 6 3 4 1. Winch for rope 2. Winch skid 3. Drilling platform 4. Telescopic stabilizer 5. Hoist with rope 6. 19 mm dia rope 7. Automatic hole real 8. Rope hole 5 Upper Level Blasting in progress 2 1 2 8 1 1 – Ladder 2 – Ventilation duct 3 – Compressed air pipe 4 – Water pipe 5 – Broken muck 6 – Partition timber 7 – Stoper drill 6 Drilling 0.9 m 2m Plan 1 – Stage bar 2 – Planks 3 – Stoper drill (a) Open raising Plan 7 3 7 (c) Raising with the Jora Lift Blasting round (d) Drilling with blasthole drifters hole length 10–30 m & dia. 50–100 mm. Long-hole raising Boring head Side grippers 5 Drilling with large blasthole drifter. Hole length 25–100 m & dia. 100–200 mm. 1 4 Tail grippers Control panel Power box Transformer 3m 3 2 Cable reel Shotcreting equipment Delay no. (1 to 5) 165 mm – dia. hole 3m (e) Drop raising Muck Disposal Arrangement (f) Application of borer for driving inclines Figure 13.4 Schematic presentation of various raising techniques. output. Earlier these methods were very popular and even today these are almost a mandatory for driving the blind raises of short lengths. However, the raises that have accesses at their both ends can be driven quickly and economically with the advent of modern methods, as discussed below. 13.7 RAISING BY THE USE OF MECHANICAL CLIMBERS: JORA HOIST4,10 In a situation where two levels are available a method known as Jora hoist was developed in the past.10 The method consists of drilling a large dia. hole at the center of the intended raise to get through into the lower level (fig. 13.4(c)).4,10 From the upper level © 2005 by Taylor & Francis Group, LLC 336 SURFACE AND UNDERGROUND EXCAVATIONS a cage is suspended using a steel rope that can be hoisted up and down using a winze. This arrangement was known as Jora hoist. The cage has got a flat surface at its top, which is used as the working platform to carry out drilling and blasting operations. With the jack mounted in the sides, the cage can be fixed against the raise sides. While drilling a round the parallel holes are drilled around the central hole, which act as a free face. Before blasting, the hoist is lowered down in an access specially driven to hold the hoist. This practice suffered with number of disadvantages, such as: requirement of accesses at both ends of the raise, necessity of a large capacity drill to drill the central large dia. hole, damage to the rope during blasting, slow and tedious hoisting operations, etc. etc. Hence the practice was discontinued, particularly when, the Alimak raise climber, described below, brought for its commercial use in the mines. 13.8 RAISING BY MECHANICAL CLIMBERS: ALIMAK RAISE CLIMBER2,14 The Alimak Company,2 Sweden, introduced this technique in 1957 and for driving the blind raises of longer lengths even today it is indispensable. The Alimak raise climber is designed by keeping sufficient safety margins with regard to the material used for its manuf...
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