COMPARISON OF SINGLE-AND MULTIPLE-UNDERREAMED BORED PILES BASED ON LABORATORY AND FIELD EXPERIMENTS

BORED PILES ARE USED EXTENSIVELY TO MEET FOUNDATION REQUIREMENTS IN SOME SOILS. THE MAXIMUM DIAMETER OF THE BELLING TOOL FOR UNDERREAMING IS LIMITED TO APROXIMATELY 3 TIMES THE DIAMETER OF THE SHAFT. THIS LIMITATION CAUSES AN UNECONOMICAL DESIGN IN SOME SOILS BECAUSE OF THE RESULTING LOW STRESS IN THE CONCRETE OF THE SHAFT. AN INCREASE IN THE AREA OF THAT PORTION OF THE PILE IN POINT-BEARING INCREASES THE BEARING CAPACITY OF THE PILE. A METHOD OF INCREASING THIS EFFECTIVE AREA IS TO CUT A BELL AT OTHER LOCATIONS ALONG THE SHAFT OF THE PILE, IN ADDITION TO THE BELL AT THE POINT. THE LABORATORY AND FIELD TESTS THAT WERE PERFORMED SO THAT THE LOAD-CARRYING CAPACITY OF SINGLE AND MULTIPLE-UNDERREAMED BORED PILES COULD BE DETERMINED ARE DESCRIBED. BELL SPACINGS AND FAILURE PLANES IN THE SOIL OF THE MODEL PILES WERE STUDIED EXTENSIVELY. THE RESULTS OF THE MODEL TESTS WERE USED IN THE TEST DESIGN OF THE FILED PILES. AN ANALYSIS OF ALL FIELD TEST RESULTS WAS MADE BY USING THE FULL AREA OF BOTH THE BELL IN POINT-BEARING AND PERIMETER OF THE SHAFT IN SKIN FRICTION. CALCULATED LOAD- DEFLECTION BEHAVIOR USING THESE ASSUMPTIONS COMPARE REASONABLY WELL WITH THE LOAD-DEFLECTION VALUES OBTAINED BY EXPERIMENTATION. MULTIPLE BELLING OF CAST- IN-PLACE PILES CAN RESULT IN ECONOMICAL DESIGN FOR MANY SOIL CONDITIONS. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: Figures; Tables;
  • Pagination: pp 80-89
  • Monograph Title: Bridges and bridge foundations
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00236241
  • Record Type: Publication
  • ISBN: 0309019672
  • Files: TRIS, TRB
  • Created Date: Jan 12 1972 12:00AM