in studying volumetric deformation of soils,we have a very famous model that is:CAM-CLAY.During introduction of this model yield surface,another surface is drawn as load surface.According to its definition,load surface:"The surface on which the current stress state always stays".What does it mean?
I don't know. I looked quickly at books by Atkinson and Bransby, and by David Muir Wood, but didn't find it. Maybe you need to go back to Schofield and Wroth's original publications?
Seems to me the current stress state is a point in q-p' space, not something that can move around on a surface. I guess it could also be a curve in q-p'-v space. Beyond that, it'a mystery to me.
If you find out, post the answer here, for my curiosity.
That definition makes more sense to me than "The surface on which the current stress state always stays." Rephrase as "The surface on which the stress state must lie any time the material is in yield"? I don't work with this stuff regularly, so it's all a distant memory from a time long ago when we couldn't look stuff up on the internet.