rupture

Hi Everybody!

I'm using YADE to reproduce a shallow foudation, but when i plot the results, i didn´ find the rupture. My graph (force versus displacement) never becomes asymptotic . My shallow foundation was simulated with two facets (6 and 7) and my soil with spheres. my script to obtain the graph is:

deltapos=0.001
x=0.001
def Carregamento():
 global x
 for i in range (6,8):
  O.bodies[i].state.pos = (0,0,0.442672-1*x)
  newton.damping = 0.2
  if unbalancedForce()<0.01:
   x+=deltapos
   myAddData()
   print x

force = 0
def calc_force():
 global force
 for b in range(6,8):
  force += O.forces.f(b)[2]
 return force

def myAddData():
 force = 0
 forca = calc_force()
        plot.addData(z1=O.bodies[6].state.refPos[2]-O.bodies[6].state.pos[2], f1=forca, i=O.iter, t=O.time)

plot.plots={'t':('f1','z1'),'f1':'z1','z1':'f1'}
plot.plot()