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+--- Thread: stress and fluids and sliding surface (/showthread.php?tid=303)
stress and fluids and sliding surface - Island Chris - 09-08-2015
Hi Gang,
Lovely daughter posted the following:
http://buam.tumblr.com/post/128205999469/i-went-out-for-lunch-with-my-dad-to-nobodys
Note that, as a nerd, I have only one side of my shirt tucked in on the video.
This is the same science as what causes earthquakes on faults. Fluid pressure should make the fault (or the table) weaker. What we saw was the opposite. This was at East Ferry deli, overlooking the bay. The video is when we went there for lunch. But, a group is there every week day for breakfast. I, and Lovely Daughter, go there for breakfast once a week. A chemist suggested it was Van der Walls force:
https://en.wikipedia.org/wiki/Van_der_Waals_force
I told him I got a "D" in chemistry and did not know what it is.
But, it may be the best explanation for what we observed. I think it is important that the table is a mesh or screen of metal.
The chemist's son will be working for US Geological Survey on tsunamis starting March 2016. The son may have to deal with me.
Chris
RE: stress and fluids and sliding surface - Skywise - 09-08-2015
(09-08-2015, 09:12 PM)Island Chris Wrote: Hi Gang,
Lovely daughter posted the following:
http://buam.tumblr.com/post/128205999469/i-went-out-for-lunch-with-my-dad-to-nobodys
Very nice write up and demonstration.
Might I also suggest looking up adhesion, and hydrogen bonding.
https://en.wikipedia.org/wiki/Adhesion
https://en.wikipedia.org/wiki/Dispersive_adhesion
https://en.wikipedia.org/wiki/Hydrogen_bond
Water is a polar molecule. Because of the shape of the molecule it has positive and negative electrical poles. Like magnets, this is what makes water molecules stick to each other (cohesion), but it also what makes water stick to other substances (adhesion).
But ultimately I think this is still all Van der Waals forces.
(09-08-2015, 09:12 PM)Island Chris Wrote: Note that, as a nerd, I have only one side of my shirt tucked in on the video.
You're just starting a new fashion trend!
(09-08-2015, 09:12 PM)Island Chris Wrote: This is the same science as what causes earthquakes on faults. Fluid pressure should make the fault (or the table) weaker. What we saw was the opposite.
I'm not sure it would be the same. On the table, you are comparing the friction between the two surfaces with and without the presence of the water. But underground, water is always present, is it not? I thought it had more to do with pore pressure; that is, the pressure of the water present in the spaces. I might have this backwards, but I thought that increased pore pressure pushed rock particles apart, reducing friction from asperities, tending toward fault failure.
Brian
RE: stress and fluids and sliding surface - Island Chris - 09-09-2015
Brian,
you are correct about pore pressure on faults. At first I thought pore pressure would be mixed up in the sliding on the table, but since there was an opposite effect, it was not pore pressure so not same as earthquakes.
Chris
[/quote]
I'm not sure it would be the same. On the table, you are comparing the friction between the two surfaces with and without the presence of the water. But underground, water is always present, is it not? I thought it had more to do with pore pressure; that is, the pressure of the water present in the spaces. I might have this backwards, but I thought that increased pore pressure pushed rock particles apart, reducing friction from asperities, tending toward fault failure.
Brian
[/quote]