Peak cavernTrenches, mud collapse

[adep]

A trip through the Trenches yesterday 9th march, revealed a number of places where clay had come away from the sides in big sections, no problem to get round, but on our return some of our group found another section had peeled off since we went through only hours earlier, this partially blocked the passage and they had use use there jammers to hack a way through, bit of a mystery as to why this is happening all of a sudden, is the clay drying out more because of increased air movement?, this is heavy stuff and could cause injury, i would recommend caution along the clay banked sections of the Trenches

 

[alastairgott]

There was a section last week that was a crawl over a block of mud, good to hear you and the Crewe crew had a good trip.

I’m now racking my brains, is it the section between Liam’s way and the hump that sends the water down the wind tunnel?
Or is it the section after the hump but before the water over welly section of the trenches?

 

[adep]

There was a section last week that was a crawl over a block of mud, good to hear you and the Crewe crew had a good trip.

I’m now racking my brains, is it the section between Liam’s way and the hump that sends the water down the wind tunnel?
Or is it the section after the hump but before the water over welly section of the trenches?

After the over the wellie section, and before the sqeezy bit before the ventilator passage

 

[pwhole]

I assume the cause is just a combination of gravity, evaporation and caver movement, rendering the clay less adhesive, and eventually its weight is more than its bond to the wall (or more clay) can stand. I guess the positive side is that the passage is gradually getting larger for future cavers - it'll be an easy stroll one day

 

[danthecavingman]

Many years ago Mark Wright and I think Richard Bartrop(?) started digging that passage rather excitedly from the top of the aven leading into the crawl, mud being thrown down the climb.... Until they realized they had actually entombed themselves and had to dig their way back out again. I'm sure Mark will remember the details......

 

[Mark]

Many years ago Mark Wright and I think Richard Bartrop(?) started digging that passage rather excitedly from the top of the aven leading into the crawl, mud being thrown down the climb.... Until they realized they had actually entombed themselves and had to dig their way back out again. I'm sure Mark will remember the details......

From JB's diary

"Sunday 12th December 1976.

Peak Cavern. A big crowd set off.

Garry, Keith and I went to Maypole Inlet to continue digging.


Bill took a party to the Treasury dig; Mark Noble, Chris, Norman, and three Orpheus members. They broke into the expected aven, and climbed 20ft to a higher tube with the aid of ladders from Perseverance Pot. The higher tube was reported to be about six feet wide and three feet high, silted after 20-30ft. It is probably now on the Wind Tunnel bedding plane and heading in the right direction."

Bill was on the outside trying to keep the bottom of the aven clear, we had to dig our way out

 

[adep]

From JB's diary

"Sunday 12th December 1976.

Peak Cavern. A big crowd set off.

Garry, Keith and I went to Maypole Inlet to continue digging.


Bill took a party to the Treasury dig; Mark Noble, Chris, Norman, and three Orpheus members. They broke into the expected aven, and climbed 20ft to a higher tube with the aid of ladders from Perseverance Pot. The higher tube was reported to be about six feet wide and three feet high, silted after 20-30ft. It is probably now on the Wind Tunnel bedding plane and heading in the right direction."

Bill was on the outside trying to keep the bottom of the aven clear, we had to dig our way out

Love stories like this!!

 

[pwhole]

There's a cartoon of that scene somewhere, but I don't have time to look further - thought it was in an old TSG Journal, but haven't found it so far. Maybe it's on the wallat the Chapel

 

[nearlywhite]

There's a cartoon of that scene somewhere, but I don't have time to look further - thought it was in an old TSG Journal, but haven't found it so far. Maybe it's on the wallat the Chapel

Now that's an idea...

 

[ChrisB]

Clay which has been has subject to pressure of overburden is described as 'consolidated'. It's squeezed until the pressure in the pores between the clay particles equals the overburden pressure. If the overburden pressure reduces (for example, if the overlying ice sheet melts or the surface is eroded) the pore pressure is then higher than the surrounding rock. The clay is described as 'over consolidated' and it's effectively stiffened by the pore water pressure (in the same way a tyre is stiffened by air pressure). When dug into, the extra stiffness initially allows it to stand unsupported, sometimes for weeks, but the cohesion between the clay particles slowly breaks down, after which the pressure pushes the clay apart and creates a fissure allowing it to flake off (to continue the tyre analogy, like a slow motion blowout). People have been killed in trenches on construction sites because they assumed that the clay would continue to stand up, not realising how it behaves, and it collapsed on them.

 

[shotlighter]

There's a cartoon of that scene somewhere, but I don't have time to look further - thought it was in an old TSG Journal, but haven't found it so far. Maybe it's on the wallat the Chapel

It's in Pitlamp's Peak Cavern book, page 60.

 

[al]

During the firrst two decades of this century, the regular passage of cavers through Colostomy Crawl and Liams Way definitely increased the flow of water through these passages. I remember one occasion travelling from the Trenches towards Egnaro Aven and being bombarded by significant waves caused by a party of cavers coming in the opposite direction (I would effectively be going upstream). Over time, this did cause some of the passages to widen where the sediment at the sides loosened and fell away and much of the displaced mud travelled downstream to collect in the Trenches. It's obviously an on-going process - the trip through to Egnaro Aven is nowhere near the struggle which I encountered the very first time I went through there.

 

[danthecavingman]

During the firrst two decades of this century, the regular passage of cavers through Colostomy Crawl and Liams Way definitely increased the flow of water through these passages. I remember one occasion travelling from the Trenches towards Egnaro Aven and being bombarded by significant waves caused by a party of cavers coming in the opposite direction (I would effectively be going upstream). Over time, this did cause some of the passages to widen where the sediment at the sides loosened and fell away and much of the displaced mud travelled downstream to collect in the Trenches. It's obviously an on-going process - the trip through to Egnaro Aven is nowhere near the struggle which I encountered the very first time I went through there.

Agreed!! First time I went through with Ben Bentham in the early nineties Colostomy was an awkward bastard, flat out and uphill towards Speedwell. So much easier now.

 

[Chocolate fireguard]

On a couple of occasions I remember very big lumps of compacted mud peeling off the LH wall, facing towards Peak. Anyone caught would certainly have been in trouble.
The consensus at the time was that the (then) new air movement was drying it out.

 

[Pitlamp]