m_world.setParticleRadius(0.15f);
{
PolygonShape shape = new PolygonShape();
shape.setAsBox(20, 4, new Vec2(0, 36), 0);
ParticleGroupDef pd = new ParticleGroupDef();
pd.flags = ParticleType.b2_tensileParticle | ParticleType.b2_viscousParticle;
pd.shape = shape;
m_world.createParticleGroup(pd);
}