Velocity effects in laboratory scale punch through experiments

Laboratory scale punch through tests on floating rubble consisting of plastic blocks were conducted. The motivation of using plastic blocks was to simplify the interpretation of results as the plastic blocks do not freeze together. The emphasis was on the methods used to derive the rubble material properties from results. In the experiments, a flat indentor platen penetrated the rubble. The indentor force as a function of its penetration was recorded. Different indentor velocities were used. The behavior of the rubble was related to the measured indentor force records. The results were compared with earlier laboratory scale punch through tests. The experiments showed, that punch through tests give results, that in some cases are difficult to interpret. The reason for this is mainly in the hydrodynamical effects arising with high indentor velocities. The results showed, that the existence of the rubble in the basin could change the hydrodynamical effects from the tests earlier used to capture them. It is shown that these effects can partly explain the shear rate dependency of the ice rubble observed in earlier work on punch through tests.