MAT Foundation sitting on Stiff Wall

[FiratPCR]

I am going to model a mat foundation, one side of which is gonna sit on very stiff (3ft wide and 22ft deep) wall. The dimensions of the matt will be 60 ft x 35ft. We can not put any restraints in STAAD.foundation. I was planning to use piles with high stiffness to respresent still wall but I should also have moment restraint since the matt would be fixed by installing dowells into the wall. I though that two sets of piles migth help by creating moment couples but I was not sure whether the piles would work compression only or works both as compression and tension springs? Could anybody know that piles also work as tension springs on STAAD.foundation or not? Also, I will appreciate if anyone has any reccomandation about how to model the stiff wall.
Thanks