How can users consider the effects of C (or Cm, i.e. Mobilized Cohesion)? Please take a butcher's at the formula of plastic shear modulus posited for the frictional soil:
Hey Navid. Check out the "new" modification of the UBCSAND proposed by Petalas and Galavi (2013) that was codded for PLAXIS 2D. This new approach, UBC3D-PLM, has interesting features, among the densification rule and the cohesion intercept and so on. However, you should know that those constitutive models were created to assess the liquefaction behavior of sandy soils, so the intercept of cohesion isn´t the best indicate for a sand.