NUMERICAL DESIGN-ANALYSIS FOR PILES IN SAND

This discussion focuses attention on how the radial effective soil stresses against the piles are influenced by the process of installation. Driving a pile causes high radial and low tangential stresses on the adjacent soil. Once the pile has penetrated beyond a given depth, the soil in the vicinity of the pile is sheared and severely vibrated by the moving pile. This treatment causes even dense sands to compact. In the case of a pile, volume changes can occur only near the pile tip and near the pile surface. Over most of the pile shaft, the compaction of the sand grains must occur without overall changes in volume. This implies that volume reduction caused by compaction must be compensated for by a volume expansion caused by elastic rebound of the radially stressed soil mass. The rebound will cause a significant reduction in the radial effective stresses. The effect of compacting the sand is to reduce the radial effective stresses, and therefore, the shaft friction, at a given depth with an increase in the driven length of the pile. The ultimate friction developed along the shaft during loading is shown for various pile lengths. Very little change in shaft friction is expected above the region influenced by the pile tip when soil compaction is not considered. Comments are made on shaft friction as related to length of driving. The experience described here emphasizes the importance of including the effects of pile installation in the design analysis.

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Filing Info

  • Accession Number: 00098645
  • Record Type: Publication
  • Report/Paper Numbers: ASCE #11339 Proceeding
  • Files: TRIS
  • Created Date: Sep 10 1975 12:00AM