Roscoe Surface, plotted by Cambridge Method.
Lines on Roscoe Surface shows same line as each stress paths, which is parallel to axis p' for Consolidated Undrain(CU), non-parallel for Consolidated Drain(CD).
Symbols on this figure are defined as followings.

p'
mean effective value = (σ1 + σ2 + σ3)/3
v
volume ratio = 1 + e
q
deviator stress = σ1 - σ3
NCL
Normal Consolidation Line
CSL
Critical State Line
Roscoe
Roscoe surface
See #gnuplot code for the physical parameters.
Own work
aokomoriuta（青子守歌）