A new large pullout-testing device has been developed and specially instrumented for characterisation of interaction between soil and geosynthetic in a pullout box by measuring wave velocity in the soil around the geosynthetic, before and at stops during pullout procedure. The paper presents some results of investigation carried out on two grids in two types of gravel, in terms of E modulus deve loped in the soil around the grid, under different vertical stresses. There is no significant influence of the grid on E value compared to non-reinforced soil, when state after compaction is tested. It is expected that after some displacement during pullout process E values might differ more, and that is next step in the research program.