Experimental group behavior of grouted deep foundations

Post-grouting of deep foundations following installation is a proven technique for enhancing axial resistance. The grouting is performed either below the tip of the foundation only (e.g., post-tip-grouted drilled shafts) or at both the side and the tip (e.g., jetted, side, and tipgrouted precast piles). The interaction of such foundations in group placement is currently unknown. This research focused on the group behavior of post-tip-grouted drilled shafts and jetted, side, and tip-grouted piles at a center-to-center spacing of three times the pile/shaft diameter. The study revealed that the post-tip-grouted drilled shafts acted independently within the group (i.e., negligible group interaction), whereas jetted, side, and tip-grouted piles behaved as a block under axial loading. It was determined that side grouting of a foundation prior to tip grouting significantly increases the grout pressure developed during tip grouting and helps in the formation of a tip grout bulb via a spherical cavity expansion process. Thus, the side and tip grouting of adjacent foundations within a group increases the confining stress and relative density of the soil mass within the group, resulting in block behavior under top-down loading. In contrast, tip-only grouted foundations showed little if any increase in radial stress and radial soil displacement, resulting in minimal improvement of the soil stiffness between shafts; as a result there was no block behavior and a negligible group effect at the tip.


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  • Accession Number: 01538372
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 14 2014 4:11PM