Understanding the boundary effects by means of numerical modelling when performing punching test on small samples

The punching test can be used to draw mechanical parameters from small pieces of rocks when it is not possi-ble to get samples big enough to perform classical tests. Small rock samples are hold by means of resins which give a certain confinement. Depending on the size of the rock piece and the mechanical behavior of the resin, the final result will be influenced by those boundary conditions. The main issue addressed here is of under-standing the boundary influence by numerical modelling and, precisely by using the explicit finite difference program FLAC. The mechanical behavior of a well-known rock, Soignies limestone, is first determined exper-imentally. Then, the action of the indenter is numerically simulated, assuming a homogeneous strain-softening material with a Mohr-Coulomb criterion.