Interaction detection problem during periodic simulation

Hi All,

I have a problem during discrete element modeling with YADE. I want to generate a pack of spherical particles in a box with frictional material model: It is working very well, no problem. With the same settings (material properties, time step ) I want to replace two parallel side of the box with periodic boundary. The definition of the periodic cell is ok, but in this case some of the spherical particles fall through the non-periodic facets of the box. I tried to change the time step, the parameters of the interaction detection, but the reason of this problem was not found.

Here is the code with periodic boundary conditions:

from yade import plot
from yade import pack, export
from yade import qt
from yade import ymport
qt.View()
import random
import time

densT = 964
ET = 6e8
nuT = .35
frictAngT = .5
eRoll = .01

EA = 2.1e8
nuA = .3
densA = 7800
frictAngA = .52

futoelem = O.materials.append(FrictMat(young=ET,poisson=nuT,density=densT,frictionAngle=frictAngT,label='futoelem'))
acel = O.materials.append(FrictMat(young=EA,poisson=nuA,density=densA,frictionAngle=frictAngA,label='acel'))
seged = O.materials.append(FrictMat(young=1000,poisson=.3,density=1000,frictionAngle=0.52,label='seged'))

O.periodic = True
O.cell.setBox((6,.1,4.5))

center = (.3,.05,1.5)

doboz = O.bodies.append(geom.utils.facetBox(center,(.1,.05,.5),wallMask=35,material='acel',wire=False,color=(.5,.5,.5)))
garat_bal01 = O.bodies.append(geom.utils.facet(((.2,0,1),(.2,.1,1),(.25,0,.5)),material='acel',wire=False,color=(.5,.5,.5)))
garat_bal02 = O.bodies.append(geom.utils.facet(((.2,.1,1),(.25,0,.5),(.25,.1,.5)),material='acel',wire=False,color=(.5,.5,.5)))

garat_jobb01 = O.bodies.append(geom.utils.facet(((.4,0,1),(.35,0,.5),(.35,.1,.5)),material='acel',wire=False,color=(.5,.5,.5)))
garat_bal02 = O.bodies.append(geom.utils.facet(((.4,0,1),(.4,.1,1),(.35,.1,.5)),material='acel',wire=False,color=(.5,.5,.5)))

sugar = .008
sugar2 = .015

felho = pack.SpherePack()
felho.makeCloud((.225,.025,1.525),(.375,.075,1.975),rMean=sugar)
particles = O.bodies.append([sphere(c,r,material='futoelem',color=(0,1,0)) for c,r in felho])

O.engines=[
        ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.3),Bo1_Facet_Aabb()],allowBiggerThanPeriod=True),
        InteractionLoop(
                [Ig2_Sphere_Sphere_ScGeom6D(),Ig2_Box_Sphere_ScGeom6D(),Ig2_Facet_Sphere_ScGeom6D()],
                [Ip2_FrictMat_FrictMat_FrictPhys()],
                [Law2_ScGeom_FrictPhys_CundallStrack()]
        ),
        NewtonIntegrator(damping=.6,gravity=(0,0,-9.81),label='newton'),
]

O.dt=.15*utils.PWaveTimeStep()

Thanks for every help!