Frongoch 14 fathom digging project - game over

[royfellows]

This is the final report on the 14fthm project as unfortunately its game over.

The project was started in 2015 after regaining the 14 fathom by installing fixed ladder up from adit level. Inbye the level was blocked by an enoumous fall, but it was possible to scramble up above the fall material to an area at the far end that had a draught. Although very unstable I that the area could be secured with steel and concrete. Initial efforts revealed that beyond the obvious fall area there had been a major slip of material which had filled in the original passage below and in effect, created a new passage at a slightly higher level. Therefore efforts were concentrated on securing the area with steel and concrete and sinking a winze at the end to regain the passage proper. Working there I became increasingly aware of the unstable nature of the area and there were several falls, one of which I very narrowly escaped as it happened while I was working under the area, but noted movement in time to get out.

I eventually halted the project due to safety concerns and discovering that the passage beyond appeared to be watered out anyway as I was digging out runny mud. Yet another fall finished this off, but I moved the sinking project forward a short distance after successfully sealing off a loose area above. Yes another fall was cleared but with growing concern I decided to halt the project and leave it for a while to see if anything moved.

Revisiting this Sunday I find a massive collapse including a boulder that must weigh over a ton. This has bent large diameter scaffold tube.

It is theoretically possible to clear this but the are too many issues. I was running out of room for stacking material which was being sandbagged, there is the safety aspect, and also the likelihood that the passage beyond is impassable anyway. So that is it.

I would strongly advise against anyone taking up this project as its likely that doing so will give the term "coffin level" a whole new meaning.

I will eventually write a full paper on the project for general interest.

 

[legendrider]

Commiserations, Roy.

Better just to walk away from a project that's becoming too fraught rather than perseverate and throw more resources at it

It was clearly telling you it wasn't at all happy, so Good Call.

One of our recent endeavours was abandoned after about 6 months of hard digging owing to excessive water, very bad air, overextended logistics paths and coffin-sized blocks of hard shale spalling off the walls and roof between shifts!

Should I ever have a generous win on the lottery, we'll be back in with an Eimco!

MARK

 

[royfellows]

If the geology is that bad a loader would not be the answer. You would be looking at heavy duty spiling and ring arching. Of all the projects that I have done on my own the most satisfying and enjoyable were the two in Cwmystwyth Lefel Fawr. Roomy conditions, volunteers (SCMC) to get materials in, and a strightforward job, once methodology had been worked out. The work you did in your mine does you great credit.

 

[legendrider]

Thanks Roy, your Steel Road was shown on the Haunted Fishtank again a couple of days ago. Nice Job.

MARK

 

[royfellows]

I want to say a bit more about Frongoch.

Recently there have been recent signs of great instability on the main site inbye of Engine Shaft. This shaft itself has its collar fallen into the shaft with a major part of the remains of the engine house on a massive rotten timber supported by nothing, and an ever widening crack in the masonry. In time it will all fall down the shaft. Williams shaft, the nearest to the main gate to the site, which is private property by the way, is on the move, running at surface and underground where once up at the 14, material was constantly falling when I was working in there. It finally stopped when a major portion of a car wedged into the 10 fthm above. The shaft was about 12 feet deep at the 14, now it’s about a yard, but slowly sinking. On surface Vaughn’s Shaft ran to a depth of about 20 feet a while back and has since been filled in. A shorter while back some old backs opened up and swallowed a few Range Rovers, the land owner dismantles them for spares and runs his business there.
The geology of this mine is quite complex. Up in 14 at the aborted dig site the lode is in form of a clay vein with a lot of pulverisation so that the ground is soft rock cemented by the clay and also subject to cross faulting. Cross faulting is abundant everywhere, in places the dip of the lode changes so that the hanging becomes the foot and vies versa. At Boundary Crosscut is one of the best examples of slickenside that I have ever seen, this testifies to the massive pressure and movement of the ground in the past. Just inbye of Engine Shaft is a massive zinc stope. To quote Thomas Garland (mining engineer) who was making an assessment of the workings in 1910:

“In the 10 fathom level west, about 8 fathoms from shaft, there is a stope in which a little blende is to be seen, but not rich enough to work at a profit. The 10 fathom level east has been driven 25 fathoms in a large lode about 3 fathoms wide, which has been worked away for blende, and the little ground left standing is not very rich. The ore ground under this level to the 20 fathom level has been worked away.

The 24 fathom level east has been driven by the present company 3? (indecipherable) Fathoms, and a stope has been worked up to the 20 fathom level which became poor.”

To be clear on the meaning of this is that there is a massive stope 9 feet wide and 60 feet deep extending for about 50 yards with more stoping up from adit level for 60 feet which possibly connects. All this is painting a picture. Its probably better that the mine inbye of Engine Shaft keeps its secrets.

 

[royfellows]

Of course, there could be some aging nutter who would install platforms and fixed ladders in the engine shaft!