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

After a bit of a slowdown after the entrance excavation, exploration is back on track.
Last year, pushing of an old lead in a cave was restarted, which initially involved capping along a horizontal rift to widen it from ~6 inches or so to a more usable size.

The rock was relatively tough, and frequently, a line of 3 or 4 caps was only enough to weaken it, needing another line to finish the job.

However, working sideways was relatively comfortable, and steady progress was made, especially on some fairly extended trips, where I managed to putting in some long solo stints while another gut was doing some science stuff elsewhere in the cave.

Eventually, we got to where the passage widened, and after disposing of some boulders in the wide section, we broke through to somewhere much larger, looking down a narrow pitch into a chamber with a good echo - possibly the best find for a long time in that particular cave.

On returning with a ladder, we dropped a short pitch onto a sloping mud floor which led to the foot of the chamber with only a dubious lead crawling down over damp mud, soon getting very low.
However, across the chamber, the rift we had entered from continued, slowly rising at walking width and ~6m high until lowering and leading to a flat-out crawl over hard clay in a bedding which soon closed down, but which had a gentle draught.

A few more trips extended the crawl for ~10m to where it rose up to meet a low passage at a T junction, with the roof being one long and wide major bed.

One way closed down to what looks like a fairly long dig - a wide gap between sand floor and roof, but only 6" high, disappearing off into the distance, and seemingly heading towards an already-known area of the cave.

The other way went crawling down a mud slope needing a little minor digging, but led onto a rather better looking lead - the floor cutting down into a trench and diving down below the bedding, with the trench being fiklled with clay and boulders at the end.

Digging down the trench progressed for several trips, mainly pulling out hard-packed clay and embedded and rocks. Many rocks seemed to be more or less in-situ, with the rock below the major bedding mentioned earlier being somewhat weaker and more prone to fracture.

Eventually, the roof changed from gently dipping to sharply rising, but we were faced with a pile of decent-sized boulders disappearing upwards.
Fortunately, we were able to bring in some decent-length scaffolding poles, and rely on the talents of the more experienced diggers.
Gradually, they worked upwards, slowly building a scaffolding cage and removing rocks, until they got back up to a wide passage with a bedding roof, with a decent-sized crawl over mud heading off.

Only a few metres ahead, the roof raised by 50cm, and looking back it could be seen that the initial bedding roof was rather less pleasant than it had first seemed.

However, while the roof carried on level, it was seen that the floor just dropped away down a muddy pile of large boulders, giving a descending passage 6-8m high and 6m wide, and carrying on for a short while before the roof started to drop and the floor turned to smooth mud, with nice mud features on the floor and selenite crystals sparkling all over the walls.
Fourther down

*Further* down, the roof dropped faster than the floor level did.
The overall passage is a descending phreatic tube, probably 4-5m in diameter, but was completely filled with sediment beyond where the floor and roof met.
Therefore, digging commenced again, but even though the passage was wide and high enough for dumping spoil right from where the dig started, to preserve the quite nice mud-crack surface of the floor there, we started dumping spoil further back up the slope, where things were less scenic.

Expecting to be in for a relatively long haul, it was decided to do a good-sized excavation, and so we settled on digging out a tunnel something over a meter square, to allow easy working, especially since the roof is dropping at ~25 degrees, and digging down in a cramped dig would be a pain.
Initially, digging was largely in clay, with a few small sand lenses, and was therefore largely a case of sitting/lying back and clay-kicking. Over time and further trips, it has varied, including clay-with-boulders, clay with well-rounded stream pebbles, and quite a lot of what looks (when dug) like a pebbly soil, but which in-situ is totally spade-resistant, being concreted together enough to need blows or 'ploughing' from a pickaxe to loosen it up.

Thus far, we've been getting up to 2m a day of progress, (which is a fair amount of weight to drag uphill), and that's usually on ~7h trips - a little under an hour's travelling each way, and the rest digging.
It's a reasonably 'balanced' dig - with a total of 6 people - 4 people hauling and emptying drag-trays, and a 'digger's second' to swap tubs at the sharp end, the haulers can move and dump spoil pretty much at the rate it's dug, and things only slow down when large rocks have to be dug out or cracked.
With reasonably regular rotation, it's fairly easy to avoid people getting too bored, which is no bad thing when it's largely the same core of people on every trip.

Wanna borrow my shovel?
Might help?...

We're still going in the dig - trips aren't as frequent as we'd like but it now needs 7 or 8 people, and one or two of the core people were off for a while as a result of (non caving) injuries.

We're now further into the dig, and well into a horizontal section, which requires forced ventilation via a car battery/fan and a 50m length of wide hose to be comfortably workable. We could be anywhere between 0 and 20m from breakthrough, depending on the accuracy of the relevant surveys.

Digging is fairly consistently in easy sand now, and we're using sandbags for convenience, since even though most end up being emptied at some point on the ever-growing spoil heap up the passage with only a few used for a retaining wall, it means that we can get away with fewer people - bags can be filled at a rate which doesn't depend on the arrival of drag trays, and dumped at the top point of the haul to be emptied later, or when part of the team is on a break. It's also possible for 2 or 3 people to do an evening trip to fill bags up and movre them back some distance, with the advance members of a subsequent larger trip clearing them before the full team arrives.

Now seems to require 9 or 10 people as a comfortable minimum, due to splitting the dragging into 2 stages for convenience.

As for distance, we had to extend the air hose, and we're seemingly rather more than 50m in from the start of the excavation, which I guess explains why the spoil heap has rather taken over the passage further up, with nice sandbag terracing and boulders that used to get in the way of movement now well submerged.

Yesterday, we removed 185 sandbags of fill, which are probably something like 15kg each (must weigh some variously-filled bags at some point). Still fairly easy digging, and carrying on horizontal at the desired level, seemingly heading in the right direction.

Digging had been relatively slow in the last couple of years.

However, we finally got through to the target cave at the weekend, with the dig ending up something like 80m long (maybe a bit more).

The dig is probably about 0.7sq.m in average cross-section, which amounts to 56 cubic metres of material, totalling 100 tons, which had to be dragged an average 50m (40m in the dig itself and 10m to the unloading point for dumping).

It was definitely worth it - the passage on the other side is very impressive, and in excellent condition, having only had a handful of people in it over the space of a week a few decades ago.