h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

With various people dropping out, leaving only 2, a planned digging trip in Wales yesterday lunchtime didn't happen.

After a morning spent setting up a new PC, the two of us decided on a quick afternoon tourist trip to check out the end of an old and abandoned cave dig. A draughting entrance led straight to a winding and often flat-out passage, which after various contortions reached a place where the passage twisted vertical, and it was possible to stand and look along a tight passage a few metres to the end of the cave. On the way in, I had felt distinctly claustrophobic in one section while waiting for D. to dig out gravel from a low crawl. It seemed the only real way to progress would be by opening up the entire passage, all the way back to the entrance, probably by taking a slice off the roof.

Apparently the draught is usually very strong in summer and winter, with the outward summer druaght sufficient even to clear fumes from 'chemical widening' fast enough to allow multiple excursions in a single day. Despite the day being hot, the relatively cool air temperature wasn't enough to drive a strong draught, yet even given that, the narrow passage did feel slightly airless.

While reversing out (the only practical way to negotiate the passage), I was surprised by a sudden feeling of cold air on my face a few metres inside the entrance. What appeared to be simply a few small gaps between fallen boulders to one side of the main crawl seemed suddenly rather interesting, though dark spaces visible could have simply been gaps between fallen-in-situ boulders. A short digging later, the manageable rocks had been removed to give a better view of an interesting lead.
Progress was blocked by a large rock (~150kg+) which seemed possibly to be supporting the slab that formed a section of the roof. Given the small size of the pasage to the entrance, the lack of manpower and tools, we couldn't do anything with it, so we went back to D's for a think.

Deciding on another quick trip, we collected various implements of destruction, and returned in the evening. One near-perfect and near-silent cap reduced the rock to a dozen chunks ranging from the easy to the just-manageable, and within ~15 minutes of our return, the ex-boulder was safely outside. The roof proved not to have been dependent on the rock, after all.

Beyond, the previously-seen small voids were found to be larger than guessed, and it appears we are in the top of what might have once been a reasonable-sized passage, though with in-situ boulder infill on a possible mud floor, and a dodgy, partly-collapsed bed of rock coming out of the roof in places preventing immediate progress. However, above the dubious roof layer, the next bed of rock is ~2m thick and quite solid-looking, so the lead is *definitely* mineable for the moment, and with the main draught being with us, it's a much better prospect than the end we had originally gone in to inspect.

I can't think of anything scarier than going underground, particularly an enclosed space which may collapse or the ceiling fall on top of me

Good job we're all different.

Keep safe

A return trip on Friday pushed further into the boulders, and ended up being terminated for lack of metalwork to support the roof. Even though further progress may well require a substantial amount of mining and shoring removal, it seems a far better bet than the original dig - shifting a ton of rock from the new face is probably easier than pulling 100kg back from the old digging face at the end of the tight winding passage would have been.

There is also another interesting rift leading off from just inside the entrance in roughly the opposite direction to the new dig. The draught is very interesting, with the rift seeming to have a more consistent draught than the new dig. The rift doesn't appear to have been pushed by the original diggeres, which does seem puzzling.

With the above dig on hold whilst finalising access, we're carrying on with a Wednesday night project in one of the major caves. At teh end of a low sandy crawl, a bedding-plane passage leads a short distance to a junction, shortly after which the interesting branch is blocked by the floor rising up towards the roof.
Continuing passage can be seen on the other side, but progress is currently slow, since the rock is seriously tough - many caps don't seem to do anything, and the best ones have maybe cracked off the odd 10Kg chunk, but we are slowly advancing.
Spoil has to be dragged 15m back up the bedding plane and stacked in the wide-but-low sides of the bedding. At least the floor on the bedding-plane edges is mainly dry mud/clay, so it is possible to excavate sideways, forcing the debris further into the narrow gap between roof and floor by use of the feet. In this way, it's possible to convert a 5m wide, average 20cm-high bedding into a 1.5m wide 60cm high bedding, which is much more use for stacking spoil, assuming we manage to increase our digging rate once the rock at the end has been dealt with.