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EXPERIENCES FROM THE USE OF IN CYCLE TENDON

SUPPORT Richard Campbell

Principal Geotechnical Engineer

Blackrock Mining Solutions

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Metallurgical Coal

AGENDA

• Context

• Installing long tendon support on advance

• What the operators see as the risks in the process

• Opportunities to minimise the risks

• Geotechnical considerations

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CONTEXT

As coal miners we are all aware we have two masters, two things that rule

our business;

1. Safety of our operators & operations

2. Longwall Float or Continuous LW Production

= sustainable & profitable business

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CONTEXT

Sustainable business.

Everyone in this room will appreciate the current and ongoing battle between

Development meters V’s Longwall retreat metres

= LONGWALL FLOAT

Increasingly the trend we are seeing is Development is losing the race.

The current push for more LW cutting hours, we are seeing across the various

major companies is increasing the gap between LW and Development.

Perceived delays of any sort in the Development process is coming under intense

scrutiny – installing long tendons in cycle is a target

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Metallurgical Coal

CONTEXT

Changing Conditions

With Australian Longwall mines facing increased geotechnical challenges, poorer conditions – perhaps needing tendons on advance in code GREEN TARP conditions just to maintain safe working conditions and the on going need to increase development rates the need to install long tendon support on advance is becoming increasing topical and the focus of optimisation.

Also coal mining in Australia is going through a series of changes is the quest for more coal at lower costs, and recovering coal in new & some times difficult deposits.

All mines seem to want to go to longer and wider LW panels (6km now, 8km soon).

– Not many 300-400m wide x 6km or 8km blocks exist in nature with no structure or zones of poor strata conditions.

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CONTEXT

6 K

m +

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ASK THE OPERATORS

When asked “what would make it safer and easier to do?”

Installing long tendon support on advance in the development cycle is a potential hazard

to our operators – some operations do not allow post groutable bolts to be installed off

the CM.

A review of tendon installation related injuries and discussions with operators identifies

the following issues:

•Physically demanding tasks, in a

confined work area of the bolting

platforms on a CM

•Repetition, multiple drill rods to get to

4m, 6m, 8m up to 14m

•Pushing resin to the back of the hole

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ASK THE OPERATORS

When asked “what would make it safer and easier to do?”

Inserting the bolt into the hole, stiff cables need to be bent around the drilling

masts & manually pushing them up the hole, getting the bolt into the chuck.

Attaching the jewellery

Using the tensioning device,

• Typically heavy & needs to be lifted above shoulder height

• High pressure hydraulic linesCrush and laceration of fingers & hands

type injuries

Strains and sprains, backs & shoulders –

heavy lifting, positioning of people

Hydraulic injection from the tensioning unit

Tensioner getting stuck on the bolt

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ASK THE OPERATORS

When asked “what would make it safer and easier to do?”

Reinstalls at the last moment in the bolt install process

The cable end gets jammed in the dolly, splits the welds, cant get the tensioner on

the bolt……………….

START AGAIN – re install,

This is a cause of a great deal of grief & rework with the crews.

Two causes identified.

1. In the dollies cable spline is not robust, various type/brands on the market none

are human proof.

2. The drill pots rotate as the drill motor & mast are dropped, if the dolly is attached

this causes the welds to split.

Needs to be fixed for optimal install process.

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OPPORTUNITIES

When asked “what would make it safer and easier to do?”

The following were identified as opportunities

Remove the need for a tensioner – torque tensionable bolts

Can we get enough tension on them, is 15+t needed?

Optimise drilling tips to the actual strata conditions, faster drilling

Cable feeders to do the grunt work of getting the bolt in the hole.

Resin insertion – not fool proof

Grouting –

Is cement type material the best product to use

Replace it with something quicker and faster setting.

If on TARP red is it 24 mins, 24 hrs 48 hrs or 7 days before the grout is

hard enough to work under?

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Metallurgical Coal

OPPORTUNITIES

When asked “what would make it safer and easier to do?”

The following were identified as opportunities

TARP related support plans that use point anchored tendons (say 6m long),

then if triggers are reached the next level uses post grouted tendons (say 8m

long) – can one bolt do both? The difference in 2m of drilling is not an issue,

pulling back the CM or stopping to put them in with an air track is an issue.

Capacity of the bolts

Grout tubes – how to ensure they survive

Are cables the right tool? Extendable self drilling steel bolts (kind of like the old

“coupled bolt”)

In hard rock they use a continuous roll of cable, automated feed and length cut off

at the hole – why don’t we?

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GEOTECHNICAL

Its always a battle between not enough & too much

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GEOTECHNICAL

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GEOTECHNICAL

Are tendons the right tool for the job.– Point anchored tendons v’s fully encapsulated

• Can we fully resin encapsulate a 6m or 6m long flexi bolt off a CM?

– How stiff are they, • How far can they stretch?

• What’s acceptable strain/deformation on a tendon?

– Pretension • How much is enough/to much

Are tendons on advance really there just to slow the movement down? – Secondary support next to follow?– Or are they the final fix?