Does a stone sinking in ocean get crushed?!

[cavatina]

assume u have a thin walled steel cylinder (1 m Dia and 10 m length for example). it is anchored to the seabed. if the water depth in the location is 2000 m, the cylinder will probably be crushed by hydrostatic pressure.

now assume you let a stone submerge in an ocean with infinite depth. the stone will sink and theoritically it should be crushed upon reaching a certain depth...?
but i FEEL it wont!

does it really sink infinitely or get crushed at a certain depth?

any answers?

 

[CarlB]

No. There are rocks on the bottom of the ocean. If a rock would crush, so would a grain of sand. There is pressure deep in the ground as well, but it doesn't crush rocks.

It's not the total stress that causes a material failure, it's the shear stress, caused by difference between principal stresses. Mohr's circle helps explain that.

 

[civilperson]

Seven miles of water depth would supply 16000 psi of compression over the entire surface of the stone and have no effect on the stone. I can not find deeper water!

 

[C2it]

Since every substance, no matter how hard, has a spring rate, the stone should get slightly smaller due to the uniform hydrostatic compressive stress over its surface.

 

[gr2vessels]

cavatina,
You have figured out that anything can be crushed under sufficient pressure, that's correct. The water won't have however, sufficient pressure ever to crush an object like a rock, no matter what the density or porosity of the rock could be (the air trapped inside the rock will continuously shrink under the water pressure, until it will reach the rock's density). So the rock will sink indefinitely, to the bottom end of the water (ocean?). However, the soil pressure on the rock (few kilometers of depth) will exceed the resistance of the rock and the energy of that pressure will melt the rock turning it into lava.
By the way, the story of the cylinder crushed under water doesn't work, there are many submarines contradicting the theory...at depths of more than 5000 or 6000 m.
cheers,
gr2vessels

 

[narenr]

Yes, the external pressure crushes the stone (or any other material) as it sinks to a depth when the hydrostatic pressure is equal to the crushing strength.

The crushing strength again depends on several factors such as porosity (water fill) and shape.

The best examples are the lava and fine seabed soil.

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[Compositepro]

Interesting responses for an engineering forum. A solid stone will not be crushed by hydrostatic at ay depth. Hollow spaces can lead to crushing. Is all rock 10 miles below the surface crushed rock? (no). Pressure does not cause heat. Movement causes heat. The application of pressure and the associated strain can cause a momentary increase in temperature.

 

[BigInch]

As Mark Twain says....

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain