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of placing ground support in the raise and such raises with a smooth circular configuration is more prone to hang-ups than a rectangular raise that has been drilled and blasted.
In highly stressed, burst prone ground, an ore pass usually has to be raisebored for safety
reasons. The same reasons make placing ground support in the raise problematic.16
18.104.22.168 Ore pass lining In bad ground, ore passes are often lined with concrete. In many cases, the concrete is
faced with high strength steel liner that also provides the formwork that is required to
pour the concrete. The steel lined ore pass has proven its suitability worldwide; however,
the high cost and time required often make this design impractical.14 Different means
have been developed for placing a concrete lining to reduce the cost.
It is generally accepted that the resistance to wear of concrete and shotcrete is
mainly dependent on the aggregate employed. It has been proposed that the most economical procedure is to select an aggregate material that has a relatively high abrasion
resistance and toughness, such as: basalt, Andesite, diabase, diorite, etc. or some
metamorphosed trap rocks. The method has proven effective in South Africa and at
some locations in North America; however, the high price of the special aggregate
makes it cost-prohibitive for most applications.
In hard rock, a long glory hole is not normally lined. Instead, two glory holes are
provided near the same location for the following reasons.
● Lining a long glory hole properly is more expensive than drilling the hole.
A second raise provides the required relief to exhaust the air blast (when both raises
If one raise becomes inoperable, the second one is available. 22.214.171.124 Design consideration of rock pass/ore pass5,12 In figures 13.12(c) to (f) orepasses of different designs have been presented. Figure
13.12(c) illustrates the ore pass with midway knuckle and figure 13.12(d) an orepass
with knuckle at bottom. In figure 13.12(e) an inclined orepass with inspection raises © 2005 by Taylor & Francis Group, LLC 352 SURFACE AND UNDERGROUND EXCAVATIONS D D (a) (b)
in θ DS H L
n r n r r Mechanics of ore flow in orepass system
(Pfleder et al. 1961) W
Side wall forces
w (γ, φ, c, H, D, θ)
(γ, µ, c, φ, H, D, θ)
(γ, H, D) n Arching forces
these result from complex
relationship among all variable r w θ θ n Symbols
γ − Weight/unit volume
µ − Friction factor of ore and wall
φ − Angle of internal friction
c − Cohesive strength 60°
200–300m 160 m Chute
(c) Orepass with
(d) Orepass with
knuckle at bottom (e) Inclined orepass with
(f) Vertical circular
inspection raises and drifts
orepass Figure 13.12 Mechanics of ore/rock flow in vertical and inclined passes. and drifts have been shown. Orepass shown in figure 13.12(f) is a vertical and having
dia. of 9 m. These ore passes are fitted with chute gate of different types so that ore
flow from them can be controlled and regulated to feed dir...
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This document was uploaded on 02/12/2014.
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