This might seem somewhat strange, so bare with me.... Let's say I have an open mineshaft on my land, approx 60m depth, 8x6 metre opening at top, and I want to put a metal grid suspended on steel girders across said hole so that people can stand on and look down. Also, I want to put an access trap door (grid) that's lockable so that brave caver like people can go down, and a metal grid bat chimney so bats can get in and out without people falling down. Has this ever been done before for such a large opening, if so, can someone point me to some examples, and even better, point me to companies who do this, and even better again, the sorts of costs to carry out such an installation? Many thanks. Phil

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We built a top on the hydraulic shaft at Greenlaws mine weardale, not too dissimilar to what you propose.
We had a contractor put a 10m steel drum into the shaft then drilled it and fitted it to a reinforced concrete cap, fitted with a lockable manhole cover ontop.
Roy fellows has posted pictures of the setup as was.

Many thanks, that's really useful. I'll check out their website

The Brewery Shaft at Nenthead has a rebuilt concrete edge with an overall galvanised steel grid that includes a viewing bridge, and a trap door. The shaft is not as large as your hole, but the engine engineering principles will be the same, I presume.

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A grid of comparable size was installed over Bwlch Mine Boundary Sfat, Cardiganshire, around 10 to 15 years ago. Although the actual shaft collar was rather smaller in size than the dimensions you quote, because the top of the collar was somewhat cratered, a concrete ring beam was cast a short distance outside of the collar, resulting in a grid of dimension very comparable to the size you quote.

On top of the ring beam and spanning the shaft around four RSJs (about 12in deep) were bolted to the ring beam. On top of the RSJs and at right angles to them were bolted smaller RSJs (about 5in deep) at around 1m centres. On top of the smaller RSJs were bolted the panels of steel grids. Incorporating a hinged trapdoor and locking point would have been straightforward though was not done at Bwlch. All the steelwork was hot dip galvanized.

A steel bat castle (either circular or square) would be easy to bolt to the smaller RSJs. Support for the panels of steel grids woul have to be carefully designed around the edge of the castle.

It has been done at Wheal Peevor. The removable grill is bolted in though.

Page's Shaft at Alport, which is of pretty big cross-section, has been grilled in a manner similar to that described above using walkway grille on RSJs. I've got some photos somewhere that I'll dig out and upload.

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IIRC, there were some pretty impressive grilles over shafts on the Great Orme, built from 4" RSJ's I think, are they still there?

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Here's a rather big one too!! 😮

🔗Ystrad-Einion-Lead-Mine-User-Album-Image-93336[linkphoto]Ystrad-Einion-Lead-Mine-User-Album-Image-93336[/linkphoto][/link]

🔗Ystrad-Einion-Lead-Mine-User-Album-Image-93337[linkphoto]Ystrad-Einion-Lead-Mine-User-Album-Image-93337[/linkphoto][/link]

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Here's a rather big one too!! 😮

🔗Ystrad-Einion-Lead-Mine-User-Album-Image-93336[linkphoto]Ystrad-Einion-Lead-Mine-User-Album-Image-93336[/linkphoto][/link]

🔗Ystrad-Einion-Lead-Mine-User-Album-Image-93337[linkphoto]Ystrad-Einion-Lead-Mine-User-Album-Image-93337[/linkphoto][/link]

That was the first one that sprang to my mind....

Epically industrial it is too.... Especially when viewed from the frogs point of view lol.

This is the grill over Page's Shaft, you get an idea of the size of it form this photo and you can just about see the latticework of RSJs supporting the walkway grilles.

🔗Pages-Shaft-User-Album-Image-93339[linkphoto]Pages-Shaft-User-Album-Image-93339[/linkphoto][/link]

...and here's what's underneath the grill!

🔗Pages-Shaft-User-Album-Image-93338[linkphoto]Pages-Shaft-User-Album-Image-93338[/linkphoto][/link]

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