Why don't miners get "the bends" ?

[Ukulele_Ike]

When divers rise to the surface too quickly after working at depth, they risk “the bends,” or decompression disease.

Breathing air under pressure forces excess nitrogen into the blood and tissue, so divers ascend slowly, using regulated tables, so the body can let the gas dissolve safely. Rising too fast means the nitrogen can form micro-bubbles, which lodge in the joints, causing extreme pain and even death. An hour of hard work “on the bottom” might mean 2-3 hours for the acsent.

Laborers in the caissons building foundations for the Brooklyn Bridge also suffered from “the bends.”

How come miners, who work in the earth at far greater depths, don’t get it? There’s a simple, answer, I’m sure, but I’m not seeing it.

[Snarky_Kong]

The Brooklyn Bridge laborers were working in a compressed atmosphere. Miners aren’t.

[Colibri]

@Ukulele_Ike

How come miners, who work in the earth at far greater depths, don’t get it? There’s a simple, answer, I’m sure, but I’m not seeing it.

Water is much denser and heavier than air, so it produces a much higher pressure at equivalent depths.

[Isilder]

Going 1km up a hill doesn’t change air pressure much, and you will be fine to 5 km or so up … so you can know that going 1km down into a sort of a narrow valley, a mine, doesn’t change air pressure much.

[Colibri]

Air pressure at sea level is about 14.7 pounds per square inch. For every 10 feet you go down in water, the pressure increases by about 14.5 psi, or doubles. You don’t have to go very deep before you have a large increase in pressure.

Air pressure increase in mines on the other hand is insufficient to cause the bends.

From here:

Van der Linde et al. (1986) found no potential for daily oscillations in barometric pressure to induce adverse physiological effects among workers in deep-level operations, other than those on the ears, sinuses and teeth referred to above. They estimated that only at a mining depth greater than 6 000m would pressure oscillations be sufficient to cause decompression sickness, and that nitrogen narcosis and oxygen toxicity would only become possible at depths of 16 000 m and 22 000 m respectively.

Since the deepest mine is less than 4000 m deep, its not deep enough to cause problems.

[Ukulele_Ike]

@Snarky_Kong

The Brooklyn Bridge laborers were working in a compressed atmosphere. Miners aren’t.

How did the atmosphere get compressed within the caissons? Weren’t they open at the top?

[newme]

@Ukulele_Ike

How did the atmosphere get compressed within the caissons? Weren’t they open at the top?

No, they were sealed and air pumped in.

[Colibri]

@Ukulele_Ike

How did the atmosphere get compressed within the caissons? Weren’t they open at the top?

They were supplied with compressed air. If they hadn’t pressurized them, water would have entered through the porous sea bed below.

[Xema]

@Colibri

For every 10 feet you go down in water, the pressure increases by about 14.5 psi, or doubles.

It increases by 14.5 psi for every 10.06 meters (= 33 feet).

Yes, it doubles over the first 33 ft. But the next 33 ft adds another 50%. And the next adds an additional 25%. And so forth.

[Colibri]

@Xema

It increases by 14.5 psi for every 10.06 meters (= 33 feet).

Sorry. I meant 10 m.

[md2000]

@Xema

It increases by 14.5 psi for every 10.06 meters (= 33 feet).

Yes, it doubles over the first 33 ft. But the next 33 ft adds another 50%. And the next adds an additional 25%. And so forth.

By comparison, you have to go up 18,000 feet to get to one-half atmospheric pressure. The deepest mines (South African gold mines, IIRC) are about 10,000 feet or so. Typical mines don’t get much more than a few thousand feet. The Dead Sea is 1400 feet below sea level, and the difference in atmospheric pressure? Not much.

Patients were tested twice: at sea level (barometric pressure, 754 +/- 6 mmHg, mean +/- SD), and at the Dead Sea (barometric pressure, 791 +/- 3 mmHg), in a randomized crossover design.

1400 feet - approximately 5% more pressure… 1400 feet of air is about the same as 16 feet of water, in case you needed more proof air weights a lot less than water.

If I’m reading my dive tables correctly, you can dive to 30 feet (1 atm.) for 310 minutes without having to decompress before surfacing. (Typical dive tables indicate that you must stop for timed intervals at a series of lesser depths to decompress depending on depth and duration.)

Caissons and under-river tunnelling works were typically pressurized enough to prevent water from flooding in if there were any leaks or cracks at the the work face.

[Ukulele_Ike]

@Colibri

They were supplied with compressed air. If they hadn’t pressurized them, water would have entered through the porous sea bed below.

Thanks for setting me straight. I KNEW I shoulda finished that damn McCullough book.

[MrDibble]

@md2000

The deepest mines (South African gold mines, IIRC) are about 10,000 feet or so.

13,000 and change, actually