SIGNIFICANCE OF LAYER DEFLECTION MEASUREMENTS

A METHOD WAS DEVELOPED USING THE BENKELMAN BEAM TO MEASURE DEFLECTION OF THE INDIVIDUAL LAYERS OF THE PAVEMENT STRUCTURE. FOUR-INCH HOLES WERE DRILLED TO THE INTERFACE OF THE DIFFERENT LAYERS OF THE PAVEMENT, AND THE HOLES WERE CASED WITH PIPE. STEEL RODS WERE REINFORCED AT THE BOTTOM OF EACH HOLE, EXTENDING UPWARD TO NEAR THE TOP OF THE PAVEMENT. MEASUREMENTS WERE MADE UNDER REAR AXLE LOADS OF 12,000 TO 27,000 LBS. RELATIVE MODULUS VALUES USING LAYER DEFLECTIONS WERE CALCULATED TO COMPARE THE RELATIVE DEFLECTION OF ONE PAVEMENT LAYER WITH ANOTHER. THEORETICAL STRESS DISTRIBUTION WAS USED AS A BASIS OF THE CALCULATIONS. IT WAS DETERMINED THAT THE SIGNIFICANCE OF THE DEFLECTION TEST RESULTS DEPENDS ON THE AGE OF THE PAVEMENT. PAVEMENTS WHICH HANDLE THE LOADS FOR WHICH THEY WERE DESIGNED SATISFACTORILY, WILL BECOME TRULY ELASTIC IN A COMPARATIVELY SHORT TIME. CONSOLIDATION OR PLASTIC FLOW WILL CAUSE RUTTING IN THE TRAFFIC LANES REGARDLESS OF THE MAGNITUDE OF THE ELASTIC DEFLECTION, BUT DOES NOT USUALLY CAUSE CRACKS OF ANY KIND. CRACKS OF THE TYPE THAT CAUSE BREAK-UP ARE PRODUCED BY EXCESSIVE ELASTIC DEFORMATION. THE EXCESSIVE DEFORMATION BENDS THE SURFACE BEYOND ITS FLEXING LIMITS AND, THUS LITERALLY SHATTERS THE SURFACE. LONGITUDINAL CRACKS ARE NOT RELATED TO EITHER CONSOLIDATION OR ELASTIC DEFORMATION. THE APPARENT CORRELATION OF RUTTING WITH THE MAGNITUDE OF ELASTIC DEFORMATION IS NO PROOF THAT SUCH CORRELATION IS SOUND FOR THE REASON THAT RUTTING IS NOT RELATED TO ELASTIC DEFORMATION. IT IS CONCLUDED THAT THE DEFLECTION TESTS MADE AFTER A PAVEMENT HAS BEEN IN USE FOR A CONSIDERABLE TIME DO NOT REVEAL THE CAUSE OF RUTTING, PROBABLY BECAUSE OF CONSOLIDATION.

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  • Supplemental Notes:
    • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
  • Authors:
    • Walker, Richard D
    • Yoder, Eldon J
    • Spencer, Walter T
    • Lowry, Robert
  • Discussers:
    • Campen, W H
  • Conference:
  • Publication Date: 1962

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: pp 63-80
  • Monograph Title: Flexible pavement design and performance studies
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00206769
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: May 13 1994 12:00AM