NEGATIVE SKIN FRICTION ON LONG PILES DRIVEN IN CLAY:-RESULTS OF A FULL SCALE INVESTIGATION ON INSTRUMENTED PILES,-GENERAL VIEWS AND DESIGN RECOMMENDATIONS

THE RESULTS OF 28 MONTHS OF MEASUREMENTS OF NEGATIVE SKIN FRICTION ON TWO TEST PILES ARE DESCRIBED. THE SOIL AT THE TEST SITE CONSISTED OF 40 M OF UNIFORM NORMALLY CONSOLIDATED CLAY THROUGH WHICH THE TEST PILES WERE DRIVEN INTO UNDERLYING SILT AND SAND. THE PILES WERE INSTRUMENTED WITH A NEW ACCURATE PILE-FORCE GAUGE WHICH MADE IT PPOSSIBLE TO MEASURE THE AXIAL LOADS AND BENDING MOMENTS IN THE PILES. SETTLEMENT GAUGES AND PIEZOMETERS WERE INSTALLED IN THE TEST FIELD PRIOR TO THE DRIVING OF THE PILES. THE RESULTS SHOWED THAT NEGATIVE SKIN FRICTION CAN BE CAUSED BY REMOULDING OF THE CLAY AROUND DRIVEN PILES AND THE SUBSEQUENT RECONSOLIDATION OF THE SOIL. ALSO, VERY SMALL SETTLEMENTS CAN CAUSE SIGNIFICANT NEGATIVE SKIN FRICTION ALONG PILES. NEGATIVE SKIN FRICTION IS SHOWN TO BE A SETTLEMENT PROBLEM AND NOT A FAILURE PROBLEM. THE BEHAVIOR OF A PILE SUBJECTED TO EXCESSIVE DRAG LOADS AND THE DIFFERENCE BETWEEN PERMANENT AND TRANSIENT LOADS ARE DISCUSSED. THE EFFECTS OF DRAG LOADS ON BATTERED AND BENT PILES ARE DISCUSSED. GENERAL DESIGN FORMULAE FOR PILES CONSIDERING NEGATIVE SKIN FRICTION ARE GIVEN. WHEN SETTLEMENTS DUE TO NEGATIVE SKIN FRICTION ARE NOT ACCEPTABLE, THE NEGATIVE FRICTION CAN BE REDUCED BY APPLYING A THIN COAT OF BITUMEN TO THE PILES. /TRRL/

Language

  • English

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 44 p.
  • Serial:
    • Issue Number: 25

Subject/Index Terms

Filing Info

  • Accession Number: 00233569
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: R&d Rept
  • Files: TRIS
  • Created Date: Jun 19 1973 12:00AM