Relation between friction and dilation in Mohr-Coulomb zone model

1

I wonder why the Mohr-Coulomb zone model in 3DEC/FLAC3D/FLAC doesn’t allow the dilation angle to be larger than the friction angle?

2

Good question. It is possible for the dilatancy angle to be greater than the friction angle for certain type of soils.
@cheng do you know why?

3

From papers I have read, it appears that earlier versions of Itasca programs admitted the dilation to be larger than friction.