Problem in Deciding which Packing to use for rock slope model

Hi, I am trying to model slope with 30 degrees which is homogeneous with properties of rock(Granitic formation) and with a single joint of particular strike and dip.but I am confused in which packing to be used for my model.

Currently, I have used this packing method [1] but as soon as I have tried to execute the script for calculation of FOS using TSSR method my whole model collapses.

So can anyone please suggest me which packing should I use.

[1];O.bodies.append(pack.randomDensePack(pred,radius=radius,rRelFuzz=0.3,memoizeDb='/tmp/gts-triax-packings.sqlite',returnSpherePack=False,color=(0.9,0.8,0.6),material=mat,spheresInCell=300))

Script:

from yade import pack, export, ymport
import gts, os.path, locale

def mat(): return JCFpmMat(type=1,young=1e8,poisson=0.3,frictionAngle=radians(30),density=3000,tensileStrength=1e6,cohesion=1e6,jointNormalStiffness=1e7,jointShearStiffness=1e7,jointCohesion=1e6,jointFrictionAngle=radians(20),jointDilationAngle=0.0)

#### control parameters
mesh='iit' #name f gts mesh
sizeRatio=10. # defines discretisation (sizeRatio=meshLength/particleDiameter)

#### import mesh
locale.setlocale(locale.LC_ALL,'en_US.UTF-8') #gts is locale-dependend. If, for example, german locale is used, gts.read()-function does not import floats normally
surface=gts.read(open(mesh+'.gts'))

print 'closed? ', surface.is_closed()

#### generate packing
if surface.is_closed():
 pred=pack.inGtsSurface(surface)
 # get characteristic dimensions
 aabb=pred.aabb()
 dim=pred.dim()
 center=pred.center()
 minDim=min(dim[0],dim[1],dim[2])
 # define discretisation
 radius=minDim/(2*sizeRatio)
 print center, dim, ' | minDim=', minDim, ' | diameter=', 2*radius
 ### packing functions
#O.bodies.append(pack.regularHexa(pred,radius=radius,gap=0.,color=(0.9,0.8,0.6)))
        #O.bodies.append(pack.regularOrtho(pred,radius=radius,gap=0.,color=(0.9,0.8,0.6)))
  #non periodic packing
#O.bodies.append(pack.randomDensePack(pred,radius=radius,rRelFuzz=0.3,useOBB=True,memoizeDb='/tmp/gts-triax-packings.sqlite',returnSpherePack=False,color=(0.9,0.8,0.6),material=mat,spheresInCell=300))
#O.bodies.append(pack.randomDensePack(pred,radius=radius,rRelFuzz=0.3,useOBB=True,memoizeDb='/tmp/gts-triax-packings.sqlite',returnSpherePack=False,color=(0.9,0.8,0.6),material=mat)) # returnSpherePack=True(?),cropLayers=5 (not to use),'
 # periodic packing
      # O.bodies.append(pack.randomDensePack(pred,radius=radius,rRelFuzz=0.3,useOBB=True,spheresInCell=5000,memoizeDb='/tmp/gts-triax-packings.sqlite', returnSpherePack= False , color=(0.9,0.8,0.6)))
# returnSpherePack=True(?),cropLayers=5 (not to use),'
        ### if you want to translate the surface away from the packing
 #surface.translate(dim[0],0,0)

O.bodies.append(pack.randomDensePack(pred,radius=radius,rRelFuzz=0.3,memoizeDb='/tmp/gts-triax-packings.sqlite',returnSpherePack=False,color=(0.9,0.8,0.6),material=mat,spheresInCell=300))
#### import mesh
O.bodies.append(pack.gtsSurface2Facets(surface,color=(0.8,0.8,0.8),wire=True))

#### export packing# in a text file
export.text(mesh+'_'+str(int(sizeRatio))+'.spheres')

#sp = pack.randomDensePack(pred,radius=rMeanSpheres,rRelFuzz=0.3,memoizeDb='/tmp/gts-triax-packings.sqlite',returnSpherePack=True)
#sp.toSimulation(color=(0.9,0.8,0.6),wire=False,material=mat)