how to simulate a rigid body when use gtsPfacet and CohFrictMat

Dear all,
     I would like to create a rigid body by use gtsPfacet and cohFrictMat, and simulate the process of structure placed on soil. Firtly, I make the body free fall from a very small height, it's ok. But, when the body contacts with the particles, It has undergone tremendous deformation and even is broken. No matter how much I increase the Young's modulus , the tremendous deformation still occurs. Only when I increase the radius of gtsPFacet, the deformation reduces a lot and this body like a elastomer.
     So, I want to ask that how to set simulate a rigid body like reinforced-concrete structure with accurate structural parameters(eg. Young's modulus ,density and so on ).
     The settings of gtsPfacet and cohFrictMat in my code are below:
  O.materials.append(CohFrictMat(young=1e10,poisson=0.001,density=7460,frictionAngle=radians(30),normalCohesion=1e100,shearCohesion=1e100,momentRotationLaw=True,label='gridNodeMat'))
O.materials.append(FrictMat(young=1e10,poisson=0.001,density=7460,frictionAngle=radians(30),label='TongjiMat'))
O.materials.append(FrictMat(young=1e7,poisson=0.3,frictionAngle=radians(20),density=2650,label='spheres'))
nodesIds1,cylIds1,pfIds1 = gtsPFacet('tongji.gts',shift=(0.,-3.3,0.),scale=1,radius=radius,wire=wire,fixed=fixed,materialNodes='gridNodeMat',material='TongjiMat',color=color)

Thank you for any suggestions.

Deng