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Pile Foundations Module #9

Pile Foundations Module #9. Prepared by Dr. Randy R. Rapp July 2005. Site Investigation. Equipment: auger (hollow-stem), split-spoon sampler, Dutch cone Data sought and recorded. Types of Bearing. Friction piles In deposits with very deep bearing strata, perhaps minimal end-bearing

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Pile Foundations Module #9

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  1. Pile FoundationsModule #9 Prepared by Dr. Randy R. Rapp July 2005

  2. Site Investigation • Equipment: auger (hollow-stem), split-spoon sampler, Dutch cone • Data sought and recorded 2005, Randy R. Rapp

  3. Types of Bearing • Friction piles • In deposits with very deep bearing strata, perhaps minimal end-bearing • End-bearing piles • Compaction piles 2005, Randy R. Rapp

  4. Augering Caissons 2005, Randy R. Rapp

  5. Pile Types • Timber • Beware delivery and storage • Cast-in-place concrete • Cased • Pipe • Shell • Fluted • Uncased • “Wet” holes must be remediated 2005, Randy R. Rapp

  6. Pile Types (Cont’d) • Precast (typically prestressed) • Plant inspection may be required • Handling is critical: beware hard-to-see failures • Steel (H-pile) • Superior if splicing perhaps needed 2005, Randy R. Rapp

  7. Driving Piles • Match hammer, pile, cushions for efficiency • Impedance = ρ x c x A, potential capacity • Specified number of blows per inch driven indicates that capacity is achieved: • Wave equation analysis by instrumentation • Empirical formulas (dynamic behavior relates to static capacity?) 2005, Randy R. Rapp

  8. Driving Piles (Cont’d) • Count blows per foot, until design blow count approached • Then count blows per inch until specification achieved • Underdriving is costly, but overdriving might cause irreparable damage to any pile type—very costly • Pile heave: neighboring piles, frost 2005, Randy R. Rapp

  9. Driving H-Piles for Pile Cap 2005, Randy R. Rapp

  10. Hammer Types • Hammers • Drop • Air • Steam • Diesel • Vibratory • Leads • Fixed: A-frame • Hanging or swinging 2005, Randy R. Rapp

  11. Pile Load Tests • Load imparted to pile in gradual steps to twice design load, as settlement data recorded • Often, load removed in steps, too, to produce load-deflection curve, p. 228 • Behavior • Elastic deformation • Buckling • Puncture • Ensure multiple deflection references, in case one is lost 2005, Randy R. Rapp

  12. Pile Load Test 2005, Randy R. Rapp

  13. Inspector Duties • Review the hammer manual, if available • Be sure that the contractor is consistent: • Technique • Equipment settings • See pp. 241-44 2005, Randy R. Rapp

  14. Sheet Piling • Differences from bearing piles • Subsurface flow cutoff • Soil retention • Alignment critical: interlock usually desired • Anchored bulkheads • Soil “nails” 2005, Randy R. Rapp

  15. Driving Sheet Piles w/ Hydraulic Hammer 2005, Randy R. Rapp

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