Helps a lot where is North ??

Not marked on the map anywhere but it's pretty much orientated North at top.

thought so thanks

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If it's any help, Aber Las farm back wall (bottom left on plan) and the field boundary behind is OS grid north.

yep got that all figured out now

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I'm trying to find out at bit more about Cambrian, but to date, I have been completely unable to source the book, so am at a bit of a disadvantage.

Thus please bear with me if I have misunderstood some of what has been discussed above.

I have visited this intriguing slate mine a couple of times and have more trips planned.

(last time I was there after a night of torrential rain there was a considerable amount of water coming down the stream way and you could really feel the current! Needless to say the Martins pit waterfall was spectacular)

On to some questions the book probably won't help me with anyhow: -

I was wondering what threat, if any, the Aberlas workings pose to explorers and the surrounding area, since I understand they are flooded, with a large head of water behind the collapse in the level you get to beyond the Martin opencast workings. Is this still the situation, and if so, has it been made worse by the winter storms?

If they are a potential danger, are there plans for dewatering them?

Also, do the divers explore in this section?

There is a pair of proposed tunnels marked on the colour coded Cambrian plan which are marked with a pale grey solid lines in the general area of the western workings. What are the significance of these? Have they been constructed yet and would they be something to do with flood control?

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Another question, this time geological: - Penarth and Moel Fferna appear to be characterised by an overlying strata that doesn't look like slate, and has very regular artificial looking and more or less parallel features running along it – very noticeable when you look up to the ceiling of the high chambers in Penarth for example. I think they have formed in some kind of sedimentary rock and the slate was quarried right up to this junction between the strata. At any rate, that's what it looks like to me.

I haven't noticed this feature in Cambrian, (at least not in the parts I've been to and which are accessible to explores like me, i.e. not flooded!) I understand Cambrian is basically in the same slate formation as Penarth and Moel?

Have I just missed it, did the quarry men not extract the slate right up to this layer, or is it just not present geologically. I personally prefer the latter idea as the slate here looks as if it outcrops and much of the mine seems to be just beneath the surface. (the flooded Aberlas workings may be deeper altogether, but that's one of the many things I don't know about the place )

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I'm trying to find out at bit more about Cambrian, but to date, I have been completely unable to source the book, so am at a bit of a disadvantage.

Thus please bear with me if I have misunderstood some of what has been discussed above.

I have visited this intriguing slate mine a couple of times and have more trips planned.

(last time I was there after a night of torrential rain there was a considerable amount of water coming down the stream way and you could really feel the current! Needless to say the Martins pit waterfall was spectacular)

On to some questions the book probably won't help me with anyhow: -

I was wondering what threat, if any, the Aberlas workings pose to explorers and the surrounding area, since I understand they are flooded, with a large head of water behind the collapsed level you get to beyond the Martin opencast workings. Is this still the situation, and if so, has it been made worse by the winter storms?

If they are a potential danger, are there plans for dewatering them?

Also, do the divers explore in this section?

There is a pair of proposed tunnels marked on the colour coded Cambrian plan which are marked with a pale grey solid lines in the general area of the western workings. What are the significance of these? Have they been constructed yet and would they be something to do with flood control?

Yes, there is a big head of water behind the blockage in the haulage way... how big though, I don't know. There used to be a big head of water in Dennis quarry which was mostly drained to avert similar fears I believe.

Divers have been in there but IIRC they hadn't gone all that far as it was a bit ropey in there.

Divers have been in there but IIRC they hadn't gone all that far as it was a bit ropey in there.

Is the water pressure causing widespread de-lamination in there causing chunks of rock to fall off and contributing to general instability?

Is this western flooded section (Aberlas workings) about the same extent or perhaps a bit larger than the eastern section? Judging from the plan it looks fairly extensive. I wonder if it's all flooded or if it's possible there may be areas of chambering beyond the flooded section, or tops of chambers which have remained above the water level?

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From what I have heard, some chamber tops are open. The majority is flooded though, and travel from one chamber to another won't happen without dive bottles or a nuclear accident resulting in the subsequent growth of gills.

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Is the water pressure causing widespread de-lamination in there causing chunks of rock to fall off and contributing to general instability?

I'd have thought it's more likely that the water is holding it up 🙂

I'd have thought it's more likely that the water is holding it up :)

Quite possible, I hadn't thought about the effect of flooding on underground stability until I heard about the floor F dam in Oakeley which was drained as it was causing delamination in a ajoining chamber - devoid of water. But as you say "catbones", if most of the chambers and their neighbours are flooded, the presence of the water may actually be contributing to stability.

This is almost certainly a complicated issue with a lot of physics behind it and will likely be unique in every case



:smartass:

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Been into aderlas today through martins quarry theres not much water coming out the collapse well there wasn't but the person I was with was pulling stuff out of the collapse and the water started to increase so we got out of there 😞

Maybe the Aberlas workings should be carefully pumped out as the whole lot sounds rather dodgy to me.

Would it be possible to do, and if so are there any plans afoot to carry it out as was done a while back with Dennis pool?


On a related theme: -
I was at a mine dig this weekend in Surrey and we saw the effect of water percolating though the strata: - It had brought down sizable chunks of ceiling. Needless to say we touched absolutely nothing but retired to the pub to discuss careful further action, if any! 😮

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On the subject of hydro locking and the water stabilising the workings that is definitely what would happen if there is a blockage.

Look up Old Gunnislake Mine, it has an interesting article produced by the council.

Basically the water is holding Gunnislake village up because the pressure is holding the mine workings up. If they become unblocked the sudden escape of water and the vacuum created by it will more than likely pull the whole village down into a large crater at least this is my poor understanding of it! :thumbup: luckily no one will miss Gunnislake or most of the inhabitants of it!

Very interesting, I suppose the extent or effectivness of water stabilisation of the workings will most likely vary with the types of rock involved. Just a guess, in the meantime I will try and find the article you recommended.

And it's my understanding that the Dennis quarry which was drained (the one with the dam onto the haulage way,)is opencast, therefore the factors to be taken into consideration when it was drained would probably have been different to that of an underground site. (eg an attempt to dewater Aberlas)

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