Abstract: This paper introduces the principles and key aspects of dynamic compaction under high vacuum conditions from a case history of strengthening of dredged soil in Caofeidian area. The applicable soils and condition for dynamic compaction and vacuum surcharge methods are reviewed separately. It was decided to use the combination of dynamic compaction and vacuum surcharge methods for the soil improvement. The earth pressures and excess porewater pressure changes at various depths are evaluated during the construction. The results indicate that, the dredged soils are improved by the combinaton of dynamic compaction and high vacuum surcharge methods could have the advantage of good improvement, cost effective and construction schedule saving. The optimum time interval between the two passes of dynamic compaction is 9 days so that the pore water pressure between two adjacent compaction craters could be effectively dissipated.

Key words: Dredged Fills, Dynamic Compaction Under High Vacuum Conditions, Soil Pressures, Porewater Pressures, Results Evaluation