Abstract: If the soil is regarded as a kind of plastic material, the impacting process can be abstracted as an acting problem of the semi-infinite body under uniform distribution pressure, so we can establish proper computation model, adopt the momentary kinetics analysis in ANSYS limited analysis software to stimulate and analyze the impacting process, in order to inquiry into the bit’s cut-in depth in soil layer and the bit’s effect on soil sample in terms of bit’s structure certain and the percussive work certain. From the analytical result, we can conclude that, firstly the soil sample’s axial compression is maximum in the bit lips surface is minimum in the center part of soil sample; secondly the messais stress in the interacting place of the bit’s inside wall and soil layer is mutating ,and the stress in soil sample keeps almost in the minimum level; finally the disturbance of impacting on the soil sample is within the very fine scope.

Key words: analytical soil sample, impact deformation, ANSYS FEA, bit’s lips surface.