Background on PM4Silt

  • The PM4Silt plasticity model was developed for representing low-plasticity silts and clays in geotechnical earthquake engineering applications. Model development emphasized approximating a range of undrained monotonic and cyclic loading responses of saturated low-plasticity silts and clays that exhibit stress-history normalized behaviors, as opposed to the responses of purely nonplastic silts and sands.
  • PM4Silt builds on the framework of the PM4Sand model (homepage). They are both stress-ratio controlled, critical state compatible, bounding surface plasticity models that have been implemented as user-defined dynamic link libraries for use with the program FLAC by Itasca (homepage).
  • PM4Silt was developed by Professors Ross W. Boulanger (homepage) and Katerina Ziotopoulou (homepage) at the University of California at Davis. We appreciate hearing from users, so please do send us an email (rwboulanger at or kziotopoulou at and let us know about your applications and experiences.
  •  The other tabs on this website provide access to the user manuals, dynamic link libraries, example files, and various reference sources.

Example: single-element simulation of undrained, uniform cyclic stress loading in direct simple shear

Example: single-element simulation of undrained, strain controlled loading in direct simple shear