Interface implementation between umat user defined constitutive model format of Abaqus and User_Mod format of Plaxis finite element code. Comes pre-compiled along with clay and sand hypoplastic model implementations, can be used as a base for implementation of other constitutive models.
The original interface implementation has been developed by prof. P. A. von Wolffersdorff in 2005. It has since been further developed and updated by David Mašín.
Description of the implementation and a user manual can be found here.