Quicksand

[Mighty_Emperor]

Its great that they are showing the possibility of a dismissed anomalous event:

Swallowed by 'dry quicksand'

Thursday December 9, 2004
The Guardian

There can't be many citations of TE Lawrence's Seven Pillars of Wisdom in the annals of fluid dynamics. But Detlef Lohse and colleagues at the University of Twente, Netherlands, nod to the 1926 account of the Arab revolt against the Ottoman empire as they report the creation of "dry quicksand" which may render stories of travellers and whole vehicles being swallowed instantly more credible.

The team made dry quicksand by forcing air through a deep layer of sand in a miniature pit and then allowing the sand to settle. In doing so, they broke up what they call the "force-chain structure" of fine sand.

To see how the dry quicksand behaved, the researchers suspended a ping-pong ball partly filled with bronze grains above the pit. They then burnt through the thin rope holding the ball. To their surprise, it disappeared beneath the sand instantaneously. Though the expected splash did not happen, a more dramatic effect was seen. "A straight jet of sand shot violently into the air after about 100 milliseconds," the team writes in the journal Nature today.

Source

The paper is:

Lohse, D., Rauhe, R., Bergmann, R. & van der Meer, D. (2004) Granular physics: Creating a dry variety of quicksand. Nature. 432 (7018). 689 - 90.

Sand can normally support a weight by relying on internal force chains. Here we weaken this force-chain structure in very fine sand by allowing air to flow through it: we find that the sand can then no longer support weight, even when the air is turned off and the bed has settled — a ball sinks into the sand to a depth of about five diameters. The final depth of the ball scales linearly with its mass and, above a threshold mass, a jet is formed that shoots sand violently into the air.

I have to say that from the pictures in the paper the jet of sand is very odd indeed. The conlusion is the bit that references Lawrence of Arabia:

In nature, dry quicksands may evolve from the sedimentation of very fine sand after it has been blown into the air and, if large enough, might be a threat to humans. Indeed, reports that travellers and whole vehicles have been swallowed instantly7,8 may even turn out to be credible in the light of our results.

...........

7. Lawrence, T. E. Seven Pillars ofWisdom
(Anchor, New York, 1926).

8. Bagnold, R. A. The Physics of Blown Sand and Desert Dunes
(Methuen, London, 1941).

Lawrence of Arabia's wikipedia entry:

http://en.wikipedia.org/wiki/T._E._Lawrence

and the 7 Pillars of Wisdom:
http://en.wikipedia.org/wiki/Seven_Pillars_of_Wisdom

Available here.

This longer report casts more doubt on Lawrence's link to this topic:

December 09, 2004

Tales about sand that swallows people may have a grain of truth

By Nigel Hawkes

TRAVELLERS’ tales about being suddenly swallowed by the desert sands may not be so fantastic as they appear.

Dutch scientists have recreated conditions that may sometimes arise when very fine sand is blown by the wind and settles to form a mass so loosely packed that it behaves like a liquid, swallowing up travellers and even vehicles whole.

This “dry quicksand” could be a threat to humans, they suggest, citing T.E. Lawrence’s Seven Pillars of Wisdom as a literary source for just such an event. If so, it would be one of the few factual statements in a book full of poetic flights of the imagination.

Detlef Lohse, of the Physics of Fluids Group at the University of Twente in the Netherlands, and colleagues blew air through very fine sand in a container with a perforated base. They then allowed the sand to settle. In doing so, it trapped a lot of air which separated the grains. When they put a ping-pong ball full of bronze grains on the surface of the sand, it disappeared instantaneously.

"Objects often make a splash as they hit sand,” the team reports in Nature. “In this case, there was no splash, as expected, but a straight jet of sand shot violently into the air after about 100 microseconds.”

The final depth reached by the ball depended on its mass, and a jet of sand was produced only by a ball weighing more than 28.5 grams (1oz). Typically, a ball reached a depth more than five times its diameter, more than deep enough, were it a vehicle, to swallow it without trace.

Granular materials such as sand behave sometimes like solids and sometimes like liquids. Imagine a tipper truck filled with gravel. As it drives along, the gravel remains solid; but when it is tipped, there comes a moment when it turns into a fluid and pours from the truck.

In a famous demonstration at the Royal Institution in London a lecturer showed the same effect by blowing air through a barrel of sand that had a steel ball lying on its surface, and a tennis ball submerged at the bottom.

As the sand was turned into a fluid, the steel ball sank and the tennis ball “floated” to the surface. Professor Lohse and colleagues have gone a stage further by showing that once fluidised, sand can appear solid but behave like a quicksand.

Whether that ever happens outside the laboratory remains conjectural. While Professor Lohse cites T. E. Lawrence, he says that his acquaintance with the book comes from the film Lawrence of Arabia, where Daud, the Arab companion of Peter O’Toole’s Lawrence, does indeed disappear as they cross the Sinai Desert.

In fact, this scene was inserted by the screenwriter Michael Wilson, or so he later claimed when his credit on the movie was denied in favour of Robert Bolt, who had produced the final rewrite.

All that Lawrence had ever claimed in Seven Pillars was that Daud had died of cold.

Despite this, travellers who encounter what the Egyptians call nafash are advised to take care. Its surface can look just like ordinary sand or gravel, but warning is given by rising clouds of dust. If the nafash is more than a few centimetres thick, vehicles can quickly be bogged down and there is no way of telling how deep it is by its appearance. Whether it can actually swallow one is perhaps doubtful.

The best advice is to keep going at a good speed, making a broad unhurried U-turn to escape. The worst is to stop.

Source

 

[Philo_T]

Damn Emps, that bit about the jet rings a bell for me, but I can't for the life of me place it. I have a very visual memory of a demonstration / film that shows the exact same thing.


Possibly this "vertical jet" is more a result of the spherical body rather than any non-binding quicksand effect. Sort of like the ping pong ball balanced in equilibirum in the air jet.


Intuitively, driving a blast of air through a mass of sand should at least temporarily create a quicksand effect. Much like the purported methane bubbles in the Bermuda triangle. Whether this would have any effect lasting beyond the end of the air jet seems debatable.

 

[Mighty_Emperor]

Intuitively, driving a blast of air through a mass of sand should at least temporarily create a quicksand effect. Much like the purported methane bubbles in the Bermuda triangle. Whether this would have any effect lasting beyond the end of the air jet seems debatable.

Ah buts that the whole point of the experiment - the air blast is just to simulate the aeolian deposition of the sand and (as far as I can tell) isn't running during the experiment (they allow the sand to settle).

I'll try and extract the photos tomorrow as they are pretty nifty.

 

[Philo_T]

the air blast is just to simulate the aeolian deposition of the sand

But now I've got a killer idea of a means to defend the approach to my mad scientist's secret lair of solitude!

 

[Mighty_Emperor]

the air blast is just to simulate the aeolian deposition of the sand

But now I've got a killer idea of a means to defend the approach to my mad scientist's secret lair of solitude!

LOL - it might have the oppsite effect though as anyone who has dropped ball bearings into their corn flakes has ever found - agitating the powder/substrate will actually cause the larger heavier object to rise.

I can see the scene now:

"Curse foiled by my skimming through the powder physics textbooks!!!! I actually rescued the heroes vehicles!!!!"

 

[ARRRRRRRRGH]

Dry quick sand not a fantasy.

This site says:

Reports that travelers and even whole vehicles have instantaneously vanished by sand have often been dismissed as products of fantasy. Rightly so? Our latest experiments show that such a dry quicksand may exist, and that objects can sink up to many diameters deep into very loose, fine sand.

The stuff simply doesn't support weight.
I wouldn't even trust a tarpaulin to stay on the surface!

Take a look at the sand jet produced as the ball drops through the sand.
Bizarre.

Wasn't sure wether to put in New science, or News. So, flipped a coin, and
it landed here.

 

[ramonmercado]

[/quote]Quicksand can't suck you under

Experiments show that humans do not sink all the way into shifting sands.
Roxanne Khamsi

Although horror films frequently depict victims disappearing in quicksand, the truth is much tamer. People cannot fully sink into this type of soil, and laboratory simulations now bear out this little-known fact.

Quicksand is simply ordinary sand that is so saturated with water that the friction between sand particles is reduced, making them unable to support any weight.

The mixture most frequently appears near the deltas of mighty rivers. It can also form after an earthquake releases water from underground reservoirs. When quicksand causes the collapse of bridges and buildings, it truly can be dangerous, experts say.

The probability that a person will be completely sucked into the sand, on the other hand, is nil. "The Hollywood version is just incorrect," says Thomas Zimmie, an expert in soil mechanics at the Rensselaer Polytechnic Institute in Troy, New York.

The real danger of quicksand is that you can get stuck in it when the high tides come up.

Daniel Bonn,
University of Amsterdam, The Netherlands



Dutch courage

But scientists have not tired of disproving the myth. Daniel Bonn's quest to recreate

quicksand in the lab began on a trip to Iran.

The researcher from the University of Amsterdam saw signs alerting visitors to the danger of this grainy soil near the Namak Lake, located in the north of the country. Bonn also heard cautionary tales from local shepherds.

The warnings piqued his curiosity and inspired him to take a sample back to the Netherlands, where he and his colleagues analysed its composition.

Once they had determined the proportions of fine sand, salt water and clay in the quicksand, they mixed up larger batches of the same.

Walking on water

Bonn and his colleagues then placed aluminium beads, which had the same density as an average human, on top of their homemade quicksand. The team shook the system, and watched as this action partially submerged the beads.

An object that falls into quicksand can cause the sand particles supported by water to loose their stability and flow downwards in a liquid fashion. Bonn likens the disturbance to the toppling of a stack of neatly arranged oranges.

"An extremely small variation in stress can cause the complete collapse of this material," he says. According to measurements taken from the bead experiments, increasing the physical stress on the particles by just 1% can cause their flow speed to increase by a factor of a million, creating a downward pull. Bonn adds that getting out of the quicksand at this point is tough; the force required to pull out a foot equals that needed to lift a medium-sized car.

"The real danger of quicksand is that you can get stuck in it when the high tides come up," says Bonn. But patience can be a life-saving virtue. If you wait long enough, the sand particles settle and the buoyancy of the mixture will cause you to rise up to the top.

As proof, the beads in the experiment did in fact float, and never became more than half submerged in sand. Although each bead measured only four millimetres in diameter, Bonn says that the findings still apply to people, as they have the same density. The results from the study appear this week in Nature1.

http://www.nature.com/news/2005/050926/ ... 926-9.html

References
Khaldoun A., Eiser E., Wegdam G.H., Bonn D. Nature, 437. 635 (2005).

 

[GNC]

I thought this fact was better known? I used to have a book from the 1970s by Eric Laithwaite which included this and the way not to drown in quicksand (basically by floating).

 

[Timble2]

I think had the same book. Also remember reading about in Reader's Digest (probably at the Doctor's) many years ago.

 

[OneWingedBird]

I found this out a couple of years ago from a friend who has a fetish about being in quicksand. Apparently your boyancy in it is such that you only sink about as far as your chest.

 

[ArthurASCII]

The whole quicksand myth was exploded by the Mythbusters on their TV show years ago.

 

[escargot]

Quicksand can still kill though, by compressing your chest so you can't breathe. It doesn't have to go far above the diaphragm to do that.

 

[rjmrjmrjm]

I've been stuck up to shoulders in thick, saline silt as a child. It was terrifing and if I hadn't been helped out I think I would've been stuck.

It was freezing cold, claggy, horrid and almost impossible to move in, all I had to do was shout and pray my father could hear.

I imagine its a close as you can get to quick sand.

 

[MrRING]

What is the fictional origin of the "death by quicksand" trope in books/movies/television?

 

[EnolaGaia]

What is the fictional origin of the "death by quicksand" trope in books/movies/television?

The trope pre-dates films and TV's, going back to explorers' tales in books, newspapers, and magazines.

The earliest quicksand scene in a film apparently dates back to a 1909 Gaumont silent film titled 'Rescued from the Quicksand'.

An overview of the trope's rise and fall can be accessed at:

http://www.slate.com/articles/health_and_science/science/2010/08/terra_infirma.html

 

[MrRING]

Thanks. I wondered if it was similar to the whole "barechested male staked to the ground" trope that was popular in TV westerns back in the day and of more recent origin.

 

[EnolaGaia]

This website:

http://www.quicksandmovies.net

... is dedicated to quicksand scenes. You can access a 2004 listing of quicksand scenes there (version 25 of a long-running list compilation effort).

I've seen references to later versions with numbers as high as 28, but I'm not sure where they may be accessed.

 

[escargot]

There's a detailed description of a death by quicksand in one of Stephen King's books, possibly The Dead Zone. King is a very assiduous researcher so you'd think he'd know whereof he speaks!

 

[RaM]

I have been to 2 or 3 exercises were people have been rescued from quicksand, they do tend to end up to the chest the sand round them then tends to solidify and they cant be pulled out, one poor sod many years ago got stuck and as the tide was coming it it got to using a lot of power with horrifying results, since then it has been found that a fire extinguisher filled with water and a long metal tube on the end works, stick the tube down close to the casualty fire the extinguisher the water turns the sand back to mush and you can haule them out.

 

[Mythopoeika]

The earliest example I have read is probably 'The Strange Ride of Morrowbie Jukes' by Kipling.
A recommended read, it dates back to 1885.

 

[Xanatic*]

Isn't quicksand similar to custard, in that it acts as a solid when moving fast? So trying to lift your arms quickly in quicksand, would make the sand resist and perhaps cause a downwards movement of your body instead?

 

[Yithian]

Sorry, can we just get this straight.

You're trying to tell me that Super Mario Bros 2, World 2ㅡ1 is not realistic?

 

[escargot]

a fire extinguisher filled with water and a long metal tube on the end works, stick the tube down close to the casualty fire the extinguisher the water turns the sand back to mush and you can haule them out.

Yup, the rescue services have machines like this now.

 

[RaM]

Yep they were down here last week with one at least that's what I think it was, needed a truck and lots of other stuff to carry it and make it work likely at least 3 people, instead of a bloke with a old fire extinguisher, ho well such is progress.

 

[oldrover]

I came into contact with the aftermath of what would prove to be a fatal encounter with quicksand once. Quite literally the day after convincing my mates it was a myth.

 

[Xanatic*]

Was it one of those mates who died?

 

[Sabresonic]

I remember back in the 90s going for a jog along the beach and falling past my feet into 2 small parts of quick sands in which a shuffled out and telling my brother later on about it he said coincidentally that day he said that he went for a jog and fell in 2 small parts of quick sand and even stranger he wasn't a regular jogger ?

 

[Sharon Hill]

I remember back in the 90s going for a jog along the beach and falling past my feet into 2 small parts of quick sands in which a shuffled out and telling my brother later on about it he said coincidentally that day he said that he went for a jog and fell in 2 small parts of quick sand and even stranger he wasn't a regular jogger ?

Quicksand... not related to sinkholes but spooky geology, nonetheless. https://spookygeology.com/trapped-in-quicksand/

 

[escargot]

Quicksand... not related to sinkholes but spooky geology, nonetheless. https://spookygeology.com/trapped-in-quicksand/

When I was a kid the fillums on TV often showed people falling into quicksand. They ALWAYS died, usually watched by their horrified enemies who'd graciously tried to rescue them but been defeated by the extreme danger.

A Stephen King book has a quicksand death too.

 

[RaM]

Lots of quick sand round here, you go down then the sand starts to dry out round you
and that's it your stuck, coast guard have some old fire extinguisher's with a lance on the
end this is pushed down into the sand next the casualty and water fired down liquefying
the sand and the poor sod dragged out. Horses and riders get stuck the last two were very
lucky to come out alive. I pulled a lad and his motor bike out a few years back luckily he did
as he was told and stayed still till I got a rope if he had panicked and struggled he may have
gone down, coast guard stopped me a day or two later and told me I was in the rescue book.
Never seen a lad as exhausted as he was bet he didn't do it again.

These two needed a wash and a good rest but were very lucky.