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ANALYTICAL METHODS APPLIED TO THE MEASUREMENTS OF DEFLECTIONS AND WAVE VELOCITIES ON HIGHWAY PAVEMENTS: PART 2, MEASUREMENTS OF WAVE VELOCITIES

THE SHELL VIBRATOR WAS USED TO INVESTIGATE THE BEHAVIOR OF A NUMBER OF HIGHWAY STRUCTURES IN TEXAS. MEASUREMENTS WERE MADE OF THE WAVELENGTH AT THE FREE SURFACE OVER A RANGE OF FREQUENCIES. THE PHASE VELOCITY OF THE WAVE WAS NOT CONSTANT BUT VARIES WITH THE FREQUENCY. STUDY WAS CONDUCTED TO DETERMINE WHAT INFORMATION CAN BE OBTAINED FROM THE FREQUENCY-DISPERSION CURVES OF PHASE VELOCITY WHICH ARE OBTAINED DURING THE EXPERIMENTAL WORK. IT IS DESIRED TO DEDUCE, IN NUMERICAL TERMS, VALUES OF THE STRUCTURAL PARAMETERS, SUCH AS THE INTERFACE DEPTHS OF THE LAYERS COMPOSING THE SYSTEM AND THE ELASTIC CONSTANTS OF THE MATERIALS COMPOSING THE LAYERS. EMPIRICAL AND SEMI-EMPIRICAL METHODS OF OBTAINING INFORMATION FROM THE RESULTS ARE DISCUSSED. IT IS SHOWN THAT SOME INFORMATION CAN BE OBTAINED BY SIMPLE CALCULATIONS BASED ON THE ASSUMPTION OF A "FREE PLATE" RESPONSE. THIS ASSUMPTION NEGLECTS ANY LOSS OF ENERGY TO THE MEDIA UNDERLYING A LAYER WHICH IS ACTING AS A FREE PLATE. THE USE OF JONES'S SOLUTIONS ARE DISCUSSED. THE GENERAL PROBLEM OF A SOLUTION TO THE EQUATIONS OF PROPAGATION OF WAVES IN LAYERED MEDIA ARE DISCUSSED, WITH THE RESTRICTION THAT THE PARTICLE MOTION IS CONFINED TO A PLANE WHICH IS PERPENDICULAR TO THE FREE SURFACE OF THE SYSTEM, AND WHICH IS ORIENTED IN THE DIRECTION OF PROPAGATION OF THE WAVES. COMPUTER PROGRAMS ARE DISCUSSED FOR THE SOLUTION OF THIS PROBLEM, WITH THE RESTRICTION THAT THE RADIATION DOWNWARDS OF ENERGY (INTO THE SUBGRADE OF A HIGHWAY PAVEMENT) CAN OCCUR, BUT IS LIMITED TO A FINITE DEPTH. COMPARISONS WERE MADE BETWEEN THE RESULTS OBTAINED FOR ELASTIC MODULI BY WAVE METHODS AND THOSE FOUND USING OBSERVATIONS MADE BY MEANS OF THE DYNAFLECT. THE VALUES OF THE ELASTIC PARAMETERS OBTAINED USING THE DYNAFLECT MAY BE INCORRECT DUE TO ERRORS APPARENT IN THE DYNAFLECT. THE ASSUMPTION THAT THE WHOLE OR PART OF A HIGHWAY PAVEMENT VIBRATES AS IF IT WERE A FREE PLATE IS SUGGESTED BY THE FACT THAT THE PLOTS OF RECIPROCAL WAVELENGTH AGAINST THE FREQUENCY FORM SETS OF STRAIGHT LINES. THIS LEADS TO RESULTS WHICH ARE QUALITATIVELY CORRECT AND WHICH MAY BE USED FOR THE PURPOSE OF RANKING WITHIN A GROUP OF MATERIALS. THE HYPOTHESIS THAT THE VELOCITY AT THE FREE SURFACE OF A LAYERED STRUCTURE REPRESENTS THE PHASE VELOCITY OF WAVES AT A DEPTH EQUAL TO HALF OF THE WAVELENGTH IS TESTED BY PLOTTING THE RESULTS IN FIGURES ON THE BASIS OF PHASE VELOCITY AGAINST WAVELENGTH. IT IS SEEN THAT THE HYPOTHESIS HOLDS, IF AT ALL, IN ISOLATED CASES ONLY. THE THEORETICAL FREQUENCY-DISPERSION CURVES OF WAVELENGTH WERE OBTAINED USING THE VALUES OF THE YOUNG'S MODULI FOUND BY MEANS OF THE DYNAFLECT. REFERENCES: SURFACE WAVE TECHNIQUE FOR MEASURING THE ELASTIC PROPERTIES AND THICKNESS OF ROADS: THEORETICAL DEVELOPMENT, R. JONES, J APPL. PHYSICS 13, 21-29, 1962.

  • Supplemental Notes:
    • Res Rept 32-15F, 82 PP, 21 FIG, 1 TAB, 10 REF, 5 APP
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 1600 E Lamar Boulevard
    Arlington, TX  United States  76011
  • Authors:
    • COGILL, W H
  • Publication Date: 1969-3

Subject/Index Terms

Filing Info

  • Accession Number: 00207072
  • Record Type: Publication
  • Files: TRIS, ATRI
  • Created Date: Mar 2 1970 12:00AM