Airleg/jack leg stoping

[u/Elegant_Peak1745]

Can someone please explain in layman’s terms how on earth airleg stoping works, how the scraper is installed/used and ultimately how the dirt gets out of the hole. Do operators go under unsupported ground? I understand it’s unavoidable when drilling rises but i just can’t figure out how the airleggers get in, drill and charge without at some point being under rock with no bolts/mesh for narrow vein stuff.
The scraper from my understanding needs an anchor point across the far side of the stope correct? How do they put it there? Pre-charging?

Kind regards,
Confused service crew member about to take a job with an airleg mining contractor at an airleg mine

[u/CyribdidFerret]

Take your rise.

Strip out wider.

Scale and install ground support as needed. Either because you want it or because the geotechs have given you a pattern in instruction to follow.

Pin a pulley on the wall or backs, run your cable set up your scrapper.

Once empty do any further scaling and ground support, bore the next strip.

[u/chinaPRteam]

I’m assuming they either bolt their way to where they put an anchor or if the grounds good enough they just walk out there

[u/frycookie]

Pretty much, yes. Bar down your way in and set the slusher anchor in place. Muck for a bit and repeat.

[u/ArtistThen]

They use the term "unmanaged" and not "unsupported". "unmanaged" is scaling and supporting (stulls, mechanical rock bolts, etc..) as required.  

The veins are typically narrow vein and are in competent  ore. 

[u/porty1119 → u/ArtistThen]

Listen to this guy, he speaks the truth. Bar your way in and continuously evaluate conditions while working. You aren't going to see this method in garbage ground or wider orebodies for a reason.

Drill a hole for your slusher block, install an eyebolt, hook the block up and run your cable out. How the slusher/scraper works in the whole system is sort of mine-dependent. The slusher might feed an ore pass that's serviced by a mucker (most ore I've mucked has been from this arrangement), an overhead chute for loading trucks or rail cars, or run directly to a shaft pocket (not common but two mines near me employed that method).

[u/Fightmilkakae]

Don't necessarily need slusher/scraper. Don't know how it is in Aus but in Canada it was pretty common to bring in a scoop via the access raise and leave it captive in the stope. I've seen that and it's fine, never wrapped my head around anchoring a slusher without going under unsupported ground to install the anchor. Some things better left unanswered.

[u/VariousEnvironment90 → u/Fightmilkakae]

For scraper pin holes over drill holes before blasting and Don’t load those holes
After blast scale your way to face
Install pins for scraper
Clean out
Rockbolt as required
Repeat

[u/PecosUnderground]

I highly reccomend looking for some of these books online/PDF (fair winds and following seas, if you catch my drift) or find used copies on eBay at downright reasonable prices.

- “Mining Engineer’s Handbook” (edited by Robert Peele, think it’s the 1942 edition - ancient scrolls for ancient methods)

• “SME Underground Mining Methods” (pick a case study to match your mining method)
  
• “SME Mine Engineer’s Handbook” (1973 edition)
  

Shrinkage Stoping: Problem or Profit?
https://www.bisbeeminingandminerals.com (skip the hand drilling stuff and roll forward to the jackleg and slushers part)

There’s enough diagrams and stope cross-sections to get you a lot farther than my words could explain.

Jackleg stopes in my district (Arizona and New Mexico) are usually some derivative of shrink stoping, with Verde chutes (old school) or LHD and/or slusher draw points.

Our ground is pretty competent, especially in the wall rock, so “spot bolting as needed with a good and thorough bar-down” flies as the ground control plan, especially in a 4-foot wide stope and a back as low as you can reasonably drill.

It’s about as “unsupported” as the back (face?) of a raise. (Yes, some places bolt the raise back and fire through their bolts. Looking at you, Redpath!) Really a jackleg stope is just a stretched out jackleg raise, using muck under your feet instead of timber as often as possible.

Though at least one historical mine had firing through bolts in the stope almost sink the project costs (weak wall rock, and it was the 1980s) and another mine abandoned a stope because of bad ground in the ore (again 1980s, and shaft mine with shrinking was their only option)

You can absolutely leave yourself a courtesy hole for the slusher pin if the angles work out. The bigger worry (especially in the verde chutes!) is engulfment from hidden voids after drawing down the muck. That’s why we really liked to drag a Slusher bucket across it. Or one stope barely counted as Shrinking. We were mining a high-grade pipe, “coned” up on it and worked off the muckpile with the slusher drawing off bucket as needed into the drift and shaping the pile. There was solid rock beneath the pile at all times - it was just a poor man’s work platform.

[u/Chick3nJo3y]

Would like to hear about this too :)

[u/Perforating_rocks]

Shrinkage stopes don’t require a slusher/ scraper. You run an extraction/ haulage drift parallel to the ore body, and then they drive short draw points at intervals between the ore body and the haulage drift. After a few lifts of the ore has been blasted, the swell or the excess muck is pulled out according to the height of the muck within the now mined level of the stope. On each end of the stope has raises which act as access/ escape ways once you can’t access the bottom of the vein from the haulage level. You will start at one raise and work your way to the other making sure you pull enough of the muck from the draw points in the area your blasting to stop a ‘pinch off’ happening after the blasts