Densification of granular soil by dynamic compaction

Land reclamation often involves the placement of loose granular soil by means of hydraulic filling. Sand fill formed by hydraulic filling generally does not allow densification by surface compaction methods because of their limited depth of influence. Loose granular soil is susceptible to liquefaction upon the impact of dynamic forces. Even under static conditions, loose granular soil may be subjected to bearing capacity failure and large settlements, because of its low shearing resistance and high compressibility. Various densification methods are used for improving such soils to increase the friction angle and elastic modulus. Several methods of deep compaction are available for such applications; among these, dynamic compaction is one of the most effective ways of densifying granular soils to a significant depth. However, the success of dynamic compaction is affected by many factors, several of which are not yet fully understood. This paper deals with the dynamic compaction densification method utilised at the Changi East reclamation site in Singapore for the improvement of reclaimed sand fill. Field data collected are used as a basis to investigate the effectiveness of the densification method and the effect of various influencing factors critical to the success of dynamic compaction treatment.