This section describes commands that are used to construct uniaxial materials for p-y, t-z and q-z elements for modeling soil-structure interaction developed at UC Davis.
There is available documentation on UCD COmpGeomech work within OpenSees framework at:
http://sokocalo.engr.ucdavis.edu/~jeremic/OpenSees/UCD_CG_OpenSees_Commands_2up.pdf
Also, there is a more in depth writeup (lecture notes) at:
http://sokocalo.engr.ucdavis.edu/~jeremic/CG/CompGeomechanicsLectureNotes.pdf