One Team One Vision With Pride

Tunnel Support

Les Gardner

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Disclaimer

The material in this presentation is for information purposes only.

The material has been prepared for ease of communication, rather than

technical correctness, and should not be considered in isolation or as

the final word on the subject.

The photographs shown may show conditions and activities that are not

necessarily accepted practice, and their source will remain anonymous.

The opinions are those of the author, and may not necessarily represent

the official viewpoint of Impala Platinum Limited.

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Basics

Primary support

Installed at the working face by development crew

Typically some type of tendon (bolt) in a set pattern

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Primary support example

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Basics

Primary support

Installed at the working face by development crew

Typically some type of tendon (bolt) in a set pattern

Secondary support

Installed behind the face by specialist crew

Typical examples include shotcrete, meshing and lacing

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Secondary support examples

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Basics

Primary support

Installed at the working face by development crew

Typically some type of tendon (bolt) in a set pattern

Secondary support

Installed behind the face by specialist crew

Typical examples include shotcrete, meshing and lacing

Tertiary support

Installed as rehabilitation / consolidation by specialist crew

Typical examples include sets, arches, void filling, cable anchors

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Tertiary support examples

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Functions of different types / units

Tendons / bolts - Pin loose blocks, reinforce tunnel “skin”

Mesh and lacing - Provide areal coverage, keep smaller

blocks from falling out, allow “yielding” capability

Cable anchors – extend reinforced tunnel “skin”, suspend

beam above tunnel, consolidate different layers

Shotcrete / Thin Sprayed Liner – provide sealing, keep

“rock fabric” intact between tendons / bolts

Steel arches / ring sets – create artificial tunnel “lining”,

provide yielding ability in “squeezing” ground conditions

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The correct support – at the right time!

Frequency of Falls of Ground from the face on Development

0

100

200

300

400

500

600

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-20

Distance from the Development Face

No.

of F

OG

's

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Blocky ground conditions No 1

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Blocky ground conditions No 2

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Fractured conditions No 1

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Fractured conditions No 2

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Wedges that fall out

Simplistic model – blocky ground

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Simplistic model - fractured rock

Stress fractures

Joints

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Mindmap for areal support

Geotechnical condition

Injury risk

Protect peoplein face

Remove peoplefrom face

Stability risk

Support system design

Excavation profile

Mechanisation Shotcrete on face

May only need bolting

Temporary areal support on face,

follow-on shotcrete

Cycle time delays

May not be ideal shape

Logistical and practical issues

Areal support in back area, but may need on face

Risk not totally eliminated

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Blocky ground – Full Areal coverage

Potential risk reduced to the absolute minimum

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Fractured rock – full areal coverage

Footwall-to-footwall shotcrete will eliminate the potential of toppling

of sidewall slabs created by

stress fracturingand/or

blocky ground

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Shotcreted haulage

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Shotcrete - benefits and penalties

Benefits: Effective long-term sealant and support

If on face, full-time areal coverage for mining crew• Reduced exposure to unsupported rock

• Reduced rock-related risk, improved safety performance

Penalties: Logistical implications (shaft, material)

Longer mining cycles, require better planning

Delays to project programme

Increased cost of project

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Why Thin Sprayed Liners?

Ongoing development of these products

Shorter spray times 30 minutes for TSLs versus 130 minutes for shotcrete

Drastic reduction in material required 1 or 2 bags/m2 for TSL versus 7 or 8 bags/m2 for shotcrete

Simple logistics One bag, one bottle mix in most cases

Reduced impact on mining cycle

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Impala TSL trial progress

Eight products identified from five suppliers

Varying degrees of success, particularly blast resistance

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Example of product on trial

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Example of product on trial

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Example of product on trial

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Example of product on trial

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Impala TSL trial progress

Eight products identified from five suppliers

Varying degrees of success, particularly blast resistance

Three products selected for extended trial

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The good…

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And the bad…

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Impala TSL trial conclusions to date

Some of the benefits proven:

Less material

Shorter application time

BUT…

Not as simple as it seems

Marginal product for the current application

Shotcrete supplement, not replacement

Supplier / applier liaison issues