It is the process of expelling only the air out of the soil mass by any suitable method. This process involves completely different mechanism against the similar consolidation process. The compression process takes less time and the maximum soil density is achieved at a certain water content. This water content is called as 'Optimum Moisture Content' or simply known as 'OMC'. In this process, though it is possible to get the soil density theoretically, but merely it is possible practically.