A comparison of foundation compaction techniques

Abstract

Soil investigation programs established the presence of locally loose to medium dense noncohesive foundation materials at three major industrial project sites. It was neccessary to densify these materials to ensure that unacceptable differential settlements did not occur between separate foundations and to reduce the potential for liquefaction of the looser zones in the event of seismic disturbance. Horizontal ground accelerations of 0.05, 0.1, and 0.3 g were used in the respective seismic analyses for the three sites. Four different techniques for in-place compaction were employed to densify the loose to medium dense soils: vibro and impact compaction, compaction piling, and deep blasting.Site descriptions and soil parameters measured are presented. A short explanation of design considerations and production work procedures is followed by a detailed comparison of the improvements obtained, measured in terms of standard or static cone penetration resistance and true relative density. Problems encountered and phenomena observed during performance of the work are described, such as the time-dependent strength increase in disturbed sands. Key words: compaction piling, deep blasting, impact compaction, vibrocompaction, foundation, penetration tests.