Easy Dilatation of Material Problem

[Nexttime35]

Homework Statement

Given that a rock is 60% porous, and if it's subjected to a large pressure that closes the pore spaces of the rock, what is the dilatation

Homework Equations

dilatation = ΔV/V_o= ε_xx + ε_yy + ε_zz

The Attempt at a Solution

Is this problem as easy as it states? If the rock shrinks by 50%, such that the pore spaces close, then the dilatation would be (1-.4^3)/1 = 0.936. So would dilatation be 0.936?, where (1-.4^3) represents the change in volume?

Thanks for the help.

 

[Chestermiller]

For a large deformation like this, the dilatation should really be expressed as ΔlnV. For this case, it is ln(0.4)=-0.916