DETECTING SEASONAL CHANGES IN LOAD-CARRYING CAPABILITIES OF FLEXIBLE PAVEMENTS

PROCEDURES ARE DESCRIBED FOR DETERMINING THE LOAD-CARRYING CAPABILITIES OF EXISTING FLEXIBLE PAVEMENTS IN AREAS SUBJECTED TO FROST ACTION. FIELD STUDIES WERE CONDUCTED TO: (1) EVALUATE EXISTING PROCEDURES, INCLUDING THOSE UTILIZING IMPULSE TECHNIQUES, (2) SELECT THE MOST PROMISING METHOD FOR DETERMINING THE LOAD-CARRYING CAPABILITIES OF FLEXIBLE PAVEMENTS DURING THE SPRING THAW PERIOD, AND (3) DEVELOP GUIDELINES FOR FIELD USE OF THE SELECTED METHOD. THE INITIAL EVALUATION OF EXISTING METHODS RESULTED IN SELECTION OF THE DYNAFLECT INSTRUMENT FOR FURTHER FIELD STUDY AND THE ULTIMATE DEVELOPMENT OF WARRANTS FOR IMPOSING LOAD RESTRICTIONS. THE DYNAFLECT EQUIPMENT MEASURES RESPONSES TO IMPULSE OR DYNAMIC LOADING. THE DYNAFLECT IS A TRAILER- MOUNTED DEVICE THAT LOADS THE PAVEMENT DYNAMICALLY AND INDICATES THE CORRESPONDING DEFLECTION AT SEVERAL POINTS ON THE SURFACE. IT IS ONE-MAN OPERATED AND TOWED BY A PASSENGER CAR. TESTS WERE MADE ON PAVEMENTS AT LOCATIONS RANGING FROM SPRINGFIELD, ILLINOIS NORTH TO DULUTH, MINNESOTA. THE TESTS SHOW THAT THE ANNUAL STRENGTH HISTORY OF PAVEMENTS IN NORTHERN CLIMATES IS DIVISIBLE INTO FOUR DISTINCT PERIODS: (1) A PERIOD OF DEEP FROST AND HIGH STRENGTH, (2) A PERIOD OF RAPID STRENGTH LOSS, (3) A PERIOD OF RAPID STRENGTH RECOVER, AND (4) A PERIOD OF SLOW STRENGTH RECOVERY. THE SECOND AND THIRD PERIODS TOGETHER CONSTITUTE THE CRITICAL PERIOD FOR FLEXIBLE PAVEMENTS. A SERIES OF CORRELATION STUDIES INDICATED THAT DYNAFLECT MEASUREMENTS COULD BE USED WITH REASONABLE ACCURACY TO PREDICT THE RESULTS OF PLATE BEARING TESTS AND BENKELMAN BEAM DEFLECTION TESTS, AS WELL AS THE CURVATURE OF THE PAVEMENT IN THE VICINITY OF A HEAVY WHEEL LOAD. THE OVER-ALL EFFICIENCY OF THE DYNAFLECT WAS JUDGED PRIMARILY ON THE BASIS OF ACCURACY, ECONOMY, AND NON- DESTRUCTIVE NATURE OF THE TESTING. THE RESEARCH RESULTS IN SUGGESTED WARRANTS, BASED ON THE USE OF THE DYNAFLECT, FOR DECIDING WHEN, WHERE, AND HOW LONG TO IMPOSE REDUCED LOAD LIMITS.

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_76.pdf
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/00775614
• 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. 37 PP, 67 FIG, 12 TAB, 10 REF, 4 APP
• Authors:
  • Scrivner, F H
  • Peohl, R
  • Moore, W M
  • Phillips, M B
• Publication Date: 1969

Media Info

• Media Type: Digital/other
• Serial:
  • NCHRP Report
  • Issue Number: 76
  • Publisher: Transportation Research Board
  • ISSN: 0077-5614

Subject/Index Terms

• TRT Terms: Bearing capacity; Benkelman beam; Deflection tests; Deflectometers; Dynaflect; Field studies; Flexible pavements; Freeze thaw durability; Frost action; Nondestructive tests; Plate bearing test; Seasons; Testing equipment
• Uncontrolled Terms: Seasonal variations
• Old TRIS Terms: Freezing thawing effects
• Subject Areas: Highways; Pavements;

Filing Info

• Accession Number: 00207074
• Record Type: Publication
• Files: TRIS, ATRI
• Created Date: Mar 9 1970 12:00AM