Bulk caving

[Bamps21]

Carrapateena mine of Oz Minerals being taken over by BHP
A similar ore body to Havieron and roughly the same cover depth.
This break through was announced this morning.
I’m presuming it’s from the sub level caving operation which is above the bulk cave.
The Decline is similar to Havieron as well, notice the conveyor layout.
They advanced their Decline far quicker than ours, ground structurally better.

With the Havieron plan changed from SLC to SLOS the backfilling with paste fill may mean Havieron doesn’t breach the surface just leaving underground chambers.

Breaching the surface with ground conditions as at Havieron may lead to large water ingress and slumping of the cover into the workings, so leaving the surface intact maybe what the mining plan is trying to achieve.

We will have to wait and see

[Bamps21]

That section on the right is a great view of what we can expect once the production Decline gets lower down .
If you expand it you can see they’ve drilled horizontally from the Decline into the ore body.
Looks a much smaller ore body than Havieron their resources and reserves look about the same as ours although the cu grades are far higher.

65% of their resources are below the cut off grades in the bulk caving.
We haven’t had those sort of figures at Havieron but you would have to add them to our resources if we added 65% of ore below cut offs.
They also have not issued a dilution factor into those resources.

[Bamps21]

These details from Oz minerals were from a presentation Aug 2017.
The Decline and box cut started in 2016.
The bulk caving below had not been found at this point.
The sections show the proposed surface breakthrough of the SLC announced this morning, so that’s 5 years.

NB! There are 3 underground crusher units

[Bamps21]

Had a discussion with a mining colleague who says he doesn’t think there will be an underground crusher for the SLOS for various reasons, notably the brittle nature of the ore, the cost of installation and also the length of time involved.

I can only agree with that scenario for the top 300-400m of the SLOS project that is phase 1.

My concerns which I have shared for sometime now are the transport logistics of trucking the ore out and these have been heightened by the talk of using smaller Volvo 40 ton electric trucks.

Initially there will be an above ground crusher while cash revenues are produced.

The issue for me is the bulking factor.
This is where the solid rock is blown up into rubble and then picked up into the trucks.
This involves 2 bulking up activities, the first one will be around 30% increase in size and second one another 5-10%.
Example if you have a 3m cube of solid rock bulking up would give a 4m cubic volume for the same tonnage.
When loaded into a truck it could swell to 4.5m.

The counter argument to that is any large lumps will be broken up by further explosives or either jaw crushers on a 360 machine.

Well I don’t think that will happen for 2 reasons:- the mine and industry in general is going for more automation ie less man power and secondly the rate of tonnage required per hour 24/7 to achieve 3m ton per year.
3m ton equates to around 350t per hour, there wouldn’t be time to break individual lumps up.

Bulking factor is greater with varying sizes of rock down to dust/ fines.
These fines do not fill up every void.
What needs to happen is to have a uniform size of ore fragments down to dust to reduce the bulking.

The initial stages the ore will be loaded on to the trucks and taken to the surface primary crusher.
Every metre cube will take more trucks to get it to surface.

This activity will not be right going forward or lower down as the turnaround times for each truck increases.

Early revenues will cover the cost of the underground crushers.
They will pay for themselves by requiring less trucking distances.
While the top zone is being mined the Decline will be going down deeper giving time for the crushers to be purchased and installation.

Crusher sizes depend mainly on the tonnage rate per day
3m t pa or about 8,500per day costs vary between $1m -5m
Installation costs could be as much as 6 times the cost of the crusher depending on sizes.
A crusher for the SLOS would be smaller than for a bulk cave operation due to the tonnage rate.

[Bamps21]

Range of crushers
https://m.made-in-china.com/product/Hyd ... 15302.html

[Bamps21]

Rock crushing rule of thumb
https://www.911metallurgist.com/blog/cr ... -of-thumbs

[RationalAssessor]

Hey Bamps - Thanks for the notes below. Quick Question for you.

There are currently 2 trains at Telfer which are (I think) significantly underutilised and inefficient due to the grade of ore being fed from Telfer.

Presently, the plan is to transport by road all of the ore from Havieron to be processed at Telfer which gives rise to the crushing points you bring out below.

Alternatives which have been discussed before are a conveyor being installed (hopefully powered by green energy) or, indeed moving one of the trains lock stock and barrel to Havieron.
The reinstatement of Havieron once all mining has been completed could require that the hole on the ground be refilled with the waste ore which would lead to a further significant transportation of that ore back from Telfer.

As NCM are now starting to see the true size of Havieron, do you think that they may be considering implementing one of these significant changes into their mining plan. My preference would be to move the train from Telfer which would result in the waste ore being held locally and reduce Havieron reinstatement costs significantly.
It's also possible that, if they fund the move of the train from Havieron Capex, they will also reduce the reintatement costs of Telfer without drawing down on the Telfer reinstatement budget.

The sooner NCM take these types of decision and change the plan, the more economical Havieron will become as a project.
Big question is whether mix of Telfer/Havieron grades is required to improve the overall efficiency of the Paterson operation.

Would be interested in your thoughts.

Thanks and ATB - RA

[speedymeadie]

Hi Rationalassessor. The moving of Telfer processing unit to Hav has been discussed many times before. It was always decided that the costs were too great. However, with the size of Hav growing, with every drill result, we must be getting nearer to that becoming financially viable. ATB Speedy

[Mremc2]

Hi Bamps - Could the answer to the bulking factor be to send in the demolition bots?

"Miners often come across large, oversized rocks underground that need to be broken down quickly and efficiently".

https://www.australianmining.com.au/fea ... ing-rocks/

Only joking! ATB Mremc2

[Bamps21]

Hi MrEMC 2
Well the drilling machines are already down there if there are any massive lumps I would expect them to blow these up with a localised explosion. Shouldn’t need anything else.

Hi Speedie/ RA
I really can’t see them moving the plant it doesn’t make economic sense.
The tailings dam is a vast area at Telfer you can see it from the satellites the Havieron licence will be lost in its size so that restricts it being positioned at Havieron.
One thing won’t happen is the mixing of the 2 ores, Telfers will be gone by 2025 if not earlier it’s very close to be uneconomic.
I asked Shaun in London about bringing a conveyor out into the Scallywag licence and he looked at me as if to say “you can’t do that”
Well it could happen if the joint venture takes over Scallywag in the future who knows what might happen.
A conveyor will be a few years away yet.

[Bamps21]

The question of reinstating Havieron you are looking at a long time in the future.
Telfer open pit is nearly ready to be filled in, so will make perfect sense to fill it in first although I have to say I’m not sure of the logistics of doing this operation. Huge weight on top of the underground caves.

Going over to Cadia they are starting to fill in their open pit with tailings

[Bamps21]

https://im-mining.com/2019/07/05/newcre ... ng-system/

Is this why Newcrest are changing to 40ton Volvos?

[Bamps21]

A 40 ton Volvo diesel

Couldn’t find a spec for an electric truck
Payload 40.5ton
Heaped c23cu m
Less bulking factor = c15cum from compacted state =40.5ton

Struck 16.85cum
Less bulking factor =c11cum
= c30 ton @2.7 sg
= c44 ton @4 sg (NB! Too heavy)
So at 4 sg can carry only 10cum or 40 ton

342 ton ph to achieve 3m ton Pa
Divided by 30t
= 11-12 trucks per hour

@18mph
Looking about 6 trips per hour less loading times
Probably achieve 3 trips per hour
So 3-4 trucks required

[Bamps21]

This is the largest Volvo
A60h
Can carry 55ton
I’m not sure about an electric version

Newcrest have gone for the 40 ton

[Bamps21]

This is the biggest hindrance to a processing plant at Havieron.
The tailings lake.
Havieron tailings are likely to be far larger in volume than Telfers.
Blue colour is from the copper not retrieved from processing.

[Bamps21]

Placing the tailings outline over the Havieron licence there wouldn’t be a lot of room left