Viscohypoplastic model with strength anisotropy (umat and Plaxis dll)
Simulation code related to paper "Jerman, J., & Mašín, D. (2020). Hypoplastic and viscohypoplastic models for soft clays with strength anisotropy. International Journal for Numerical and Analytical Methods in Geomechanics, 44(10), 1396-1416".
For parameters of the base model, see https://web.natur.cuni.cz/uhigug/masin/plaxumat/
Additionally, the following parameters need to be set for the model, please also refer to the paper "Jerman, J., & Mašín, D. (2020). Hypoplastic and viscohypoplastic models for soft clays with strength anisotropy. International Journal for Numerical and Analytical Methods in Geomechanics, 44(10), 1396-1416". The parameters are separated to three groups, which can be used separately:
1) Rate effects (viscohypoplasticity)
Dr - a reference creep rate corresponding to the reference ASBS. Dr must be selected so that the model correctly predicts the rate-dependent positions of the normal compression line.
Iv - viscosity index. Controls the influence of OCR+ on the rate-dependent position of the isotropic and odometric normal compression lines, the rate-dependent undrained shear strength cu, and the creep and relaxation rates.
2) Strength anisotropy
β - inclination of the asymptotic state boundary surface with respect to the p-axis in the q-p plane.
3) Stress path correction
γ - inclination of the skewed stress space with respect to the p-axis in the q-p plane, it specifies the value of the stress deviator, where the stress path becomes perpendicular.
to p-axis. Can be automatically calibrated from the original stress state to maximize the effect of the LD approach.
ξ - parameter controlling the stress path shape.
