Pore dilation with increased pressure

[A_B]

Homework Statement

When walking on the wet strip on the beach, you notice the sand around your feet becoming dry for a while. Why is this?

Homework Equations

The Attempt at a Solution

Intuition says that the pressure due to your weight should squeeze the water from under your foot to the surrounding sand, making it more wet, instead, water is pulled away from the sand surrounding your feet.

I found the following in the soil mechanics page on wikipedia: http://en.wikipedia.org/wiki/Soil_mechanics"
"Foot pressing in soil causes soil to dilate, drawing water from the surface into the pores."

As I understand it, this says that by pushing on wet sand, its volume increases, since the pores dilate, How does that work?

 

[Fewmet]

Intuition says that the pressure due to your weight should squeeze the water from under your foot to the surrounding sand, making it more wet, instead, water is pulled away from the sand surrounding your feet.

I found the following in the soil mechanics page on wikipedia: http://en.wikipedia.org/wiki/Soil_mechanics"
"Foot pressing in soil causes soil to dilate, drawing water from the surface into the pores."

As I understand it, this says that by pushing on wet sand, its volume increases, since the pores dilate, How does that work?

That's really interesting. I had always assumed the mechanism was was you intuited. The discussion of your quoted passage notes that soils can do that, but not beach sand. Looking a little further I found a discussion of http://en.wikipedia.org/wiki/Reynolds%27_dilatancy" . That explains that when the grains are interlocking, they lever each other apart rather than compressing.

You have have forever changed my walks on the beach. Thanks for that.