PRESENT DESIGN PRACTICE AND CONSTRUCTION DEVELOPMENTS IN FLEXIBLE PAVEMENTS

THE TERM "FLEXIBLE PAVEMENTS" MIGHT PROPERLY INCLUDE QUITE A VARIETY OF SURFACING MATERIALS, BUT FOR PURPOSES OF THIS PAPER THEY ARE CONSIDERED AS THOSE BITUMINOUS TYPES OF SURFACES WHICH ARE MUDLESS AND DUSTLESS AT ALL SEASONS OF THE YEAR. AS A RESULT OF QUESTIONNAIRE STUDY TO THE VARIOUS STATE HIGHWAY DEPARTMENTS, SOME INTERESTING CONCLUSIONS HAVE BEEN REACHED. THE IMPORTANCE OF THE DESIGN OF SUBGRADE IS BECOMING GENERALLY RECOGNIZED AND THAT THE CORRECT METHOD OF DETERMINATION OF THICKNESS OF PAVEMENT SHOULD BE PREDICATED UPON BRINGING SUBGRADE VALUES UP RATHER THAN ATTEMPTING TO BUILD MASSIVE BASES DOWN. THE DEVELOPMENT OF TYPES OF SURFACES HAS GONE THROUGH A CERTAIN CYCLE AND IS RATHER INTIMATELY RELATED TO THE DEVELOPMENT OF EQUIPMENT. THE INFLUENCE OF TRAFFIC UNDER LOAD DISTRIBUTION HAS GREATLY MODIFIED THE DESIGN OF PAVEMENTS AND HAS MADE POSSIBLE THE EFFECTIVE CARRYING OF TRAFFIC UNDER VOLUMES WHICH WOULD HAVE BEEN DESTRUCTIVE IF THE BALLOON TIRE HAD NOT BEEN INVENTED AND BECOME UNIVERSALLY AVAILABLE ON ALL MOTOR DRIVEN EQUIPMENT. THE SELECTION OF TYPE OF SURFACE ALSO SHOULD TAKE INTO ACCOUNT ALL AGGREGATE AVAILABLE LOCALLY. COGNIZANCE SHOULD BE TAKEN OF THE FACT THAT STONE AND GRAVEL VARY IN SIZE ACCORDING TO GEOLOGICAL FORMATIONS, AND SURFACES SHOULD BE DESIGNED SO AS TO USE MOST ECONOMICALLY THE COMPLETE PLANT OUTPUT. AN ILLUSTRATION OF THIS BETTER USE OF PLANT OUTPUT, AND AT THE SAME TIME VASTLY IMPROVING THE ROAD STRUCTURE, IS THE GROWING USE OF STONE SCREENINGS OF APPROXIMATELY 1 1/2 INCHES THICKNESS AS AN INSULATION LAYER BETWEEN THE NATURAL SUBGRADE AND THE PAVEMENT PROPER. METHODS FOR ACCURATELY EVALUATING SUBGRADE VALUES ARE STILL NEEDED. SEVERAL STATES HAVE METHODS OF MAKING SUCH TESTS WHICH APPARENTLY GIVE GOOD RESULTS. ONE INTERESTING DEVELOPMENT IS THE ATTEMPT OF ONE STATE TO DESIGN THE THICKNESS OF BASE COURSES IN ACCORDANCE WITH THE SOIL CHARACTERISTICS, SUCH AS PLASTIC LIMIT, LIQUID LIMIT, ETC. AN ENCOURAGING NOTE FROM THIS REVIEW OF PRACTICE IS THE INTENSIVE ATTENTION WHICH IS BEING GIVEN TO THE DESIGN OF THE SUBGRADE, WHICH AFTER ALL MUST CARRY THE LOAD, AND WHICH UNTIL RECENT YEARS HAS BEEN ALMOST ENTIRELY OVERLOOKED AS AN ELEMENT IN PAVEMENT DESIGN. /AUTHOR/

  • Supplemental Notes:
    • Vol 19, pp 175-192, 10 TAB, 6 REF
  • Authors:
    • Gray, B E
  • Publication Date: 1940

Media Info

  • Monograph Title: Proceedings of the Nineteenth Annual Meeting of the Highway Research Board Held at Washington, D.C. December 5-8, 1939
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00233045
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Oct 3 1971 12:00AM