Abstract: This project site was backfilled with silty clayey and clayey soils with weak expansive potentials. The maximum backfill depth is 8 meters. The dynamic compaction method was utilized to improve the site.  Different dynamic compaction trial parameters and monitoring programs are used in different areas with different backfill depths. The results indicate that, the compaction energy of 3,000 kN·m and a spacing of 6 meters has a better results than those area compacted by the compaction energy of 2,000 kN·m and a spacing of 5 meters.  The depth of backfills should be considered first when the compaction parameters are to be selected. The results can be optimized by adjusting the compaction spacing, number of drops at each compaction point in the trial compactions.

Key words: Dynamic Compaction, Trial Compaction, Deep Backfills