Abstract: A one-dimensional, two-phase flow model and the intragranular stress function is used to describe the structure and its formation of compaction wave in granular material. The piston impact problem for a compressible porous solid has been solved using a simplified model neglecting gas phase effects. With this model, it is possible to obtain an solution for the compaction wave speed, final porosity, and final pressure. At low piston velocities, the compaction wave travels at speeds less than the ambient solid...