creep relax

Here is a UMAT using an  elastic viscoplastic model for soil

Modifed Cam-clay model coupled with viscosity.

ABAQUS - UMAT (Free Download for Research Purposes)

A user-defined subroutine in ABAQUS for viscous soils.

Introduction:

The ABAQUS subroutine is for viscous soils, which
usually have the following characteristics.