Rock-split granite boulders confirmed

Technique : Rock-split granite [boulders] with "cordless" SDS drill and "feathers" of 14March2024 consolidated-on. Used at "production" rate. Yes it works reliably, at predicted rate (= rapid) when sequenced in the predicted "obvious" optimal way.

Details at time of writing, as used today:

• evaluate what will be a wheelbarrow-full of rocks of acceptable (not over-) size - or 2 or 3 wheelbarrows-full, as intended
• drill oversized rocks - every intended socket (for "feathers") 6mm pilot drill to depth; every pilot hole follow 14mm drill
• all drilling (pilot and size) with water-spray so ejected material is slurry = zero dust production - also keeps drill cool - water-jet from squeezed 2Litre plastic bottle with fine hole in lid so fast fine jet into hole down drill flutes
• wash-out hole with water and spin out slurry with drill
• (noting for the drilling and for washing-out, water consumption is not high - 2Litres does many holes - so be liberal (water easily replenished in this mine - water pouring through "deads" and down shafts which can refill bottle))
• "feathers" lubricated - wedge in feathers - with graphite thin-oil spray - so lubricated but not sticky to become grinding-paste of fine silica and grease - and can wipe clean on cloth after each use
• work along rocks with their drilled sockets with the "feathers" - maybe four in use doing two split lines on two different boulders at a time if close - so can tap wedges in sequence, with the "wait" pauses listening for the cracking and tapping more as appropriate
• if intended split cracked but not separating, pick-chisel-bit in SDS drill rotation-stopped to open-up crack and split boulder apart
• move "feathers" on to next drilled sockets and split-lines; tap wedges into "feathers" and split on these lines
• etc until all sockets used and splits done
• load wheelbarrow and take along sub-level to stope, to lower in cargo-net to tramming level
• clean "feathers", drill, etc
• proceed with next series of splits

A lot of holes will drill with one 4Ah (18V) battery. Limit not in-view yet. With clearing stones away, in two hours it is difficult to use much of one battery.

Seems good-quality reputable-brand drill-bits are needed. This "cordless" SDS drill is able to make the drill-bits "work".

Whether pilot-drilling - as described above - is optimal is not yet well investigated.

As already mentioned - if use a plastic bottle with screw-top having a fine hole in it to generate a fine high-velocity "thread" of water, water consumption is not a lot. Do be generous with the water such that all ejected drilled granite is a fluid slurry.
It is to advantage if the slurry runs-away clear of the drilled hole - hence use enough water to make the slurry "thin" and fluid.

Where there is a pile of rocks, an advantage of this method is that can split rocks along chosen lines while in-situ in the pile.
As-blasted in this case (blasting done a long time previously)
That advantage is that can split off enough of a projection of a large rock so that frees the right amount of rock at the top of the pile to slide down off the pile to be removed. Safety advantage - control.

As previously said : for a task for which there was no previous satisfactory solution, what is seen is a pleasingly productive way of sending optimal-sized rocks along the level, down the stope, along the tramming level, into the skip and hoisted to surface, skip emptied at surface into another wheelbarrow and disposed of by making a wall with the rocks or filling behind already-made walls.

Where we are now, with the mine

Of the various renovation and maintenance tasks, the readiness with which boulders can be removed as handleable rocks has lead to planning what clearing of levels is the desired end-point.

(R. Smith, 21Mar2024)