How do you know it has been successful?

The geotechnical consultant may specify a variety of subsurface testing techniques to verify that the improvement has been achieved.  Unfortunately, experience has shown that in many cases, the testing does not accurately indicate the amount of improvement, unless it is done weeks or even months after the compaction is done.  The simplest, and perhaps the most reliable indication of improvement is through elevation surveys of the compaction. Area.  If the surface has been lowered, significant improvement has occurred.