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Title: DEVELOPMENT OF A PROCEDURE FOR THE DESIGN OF FLEXIBLE BASES
Accession Number: 00233089
Record Type: Component
Availability: Transportation Research Board Business Office 500 Fifth Street, NW Abstract: THE DESIGN PROCEDURE DESCRIBED IN THIS PAPER IS THE RESULT OF AN INVESTIGATION, STILL IN PROGRESS, SET UP TO ESTABLISH A RELATIONSHIP BETWEEN FIELD PERFORMANCE OF GRANULAR BASES AND BEARING VALUES OBTAINED IN THE LABORATORY BY MEANS OF THE CALIFORNIA BEARING TEST, OR MODIFICATIONS THEREOF. THE FIELD INVESTIGATION INVOLVED CONDITION SURVEYS OF BITUMINOUS SURFACES PLACED ON GRANULAR BASES, THE DETERMINATION OF THICKNESS, DENSITY AND MOISTURE CONTENT, AND NORTH DAKOTA CONE BEARING VALUE OF THE SUBGRADES. SAMPLES OF THE BASE MATERIALS AND SUBGRADES WERE SENT TO THE LABORATORY FOR ANALYSIS AND BEARING VALUES. FIELD MOISTURE AND DENSITY DETERMINATIONS WERE ALSO MADE TO DETERMINE SEASONAL AND ANNUAL FLUCTUATIONS IN BASE AND SUBGRADES. THE FIELD STUDIES REVEALED THAT FAILURES HAD OCCURRED WITHIN PRACTICALLY THE ENTIRE RANGE OF MOISTURES AND DENSITIES FOUND IN THE ROAD, WHICH WOULD INDICATE GENERALLY INADEQUATE THICKNESS OF BASE ON PLASTIC SOIL SUBGRADES. THERE WAS SOME RELATION BETWEEN MOISTURE CONTENT AND THE PLASTIC LIMIT OF SUBGRADE SOILS. LABORATORY TESTS WERE MADE USING THE CALIFORNIA BEARING TEST PROCEDURE ON SPECIMENS MOLDED AS DESCRIBED IN THE 1938 PROCEEDINGS AND ON SPECIMENS COMPACTED TO STANDARD AASHO AND MODIFIED AASHO DENSITIES. IT WAS CONCLUEDED THAT, FOR ALL METHODS OF COMPACTION USED, SOAKING OF THE SPECIMENS FROM THE TOP RESULTED IN MOISTURE CONDITIONS MORE SEVERE THAN WERE FOUND IN THE FIELD AND THAT SOME MODIFICATIONS OF THE SOAKING PROCEDURE WAS DESIRABLE. ON THE BASIS OF CONSIDERABLE LABORATORY DATA IT WA DECIDED THAT THE CALIFORNIA BEARING TEST OFFERS A PRACTICAL METHOD FOR EVALUATING SUBGRADE SOLS AND GRANULAR MATERIALS PROVIDED THAT SAMPLES ARE TESTED AT MOISTURE CONTENTS AND DENSITIES SUCH AS EXIST OR ARE ANTICIPATED ON MINNESOTA ROADS. PLASTIC SUBGRADE SOILS ARE COMPACTED TO 97 PERCENT OF AASHO MAXIMUM DENSITY AND AT MOISTURE CONTENTS EQUAL TO A PERCENTAGE OF SATURATION DETERMINED FROM THE RELATIONSHIP ESTABLISHED BETWEEN PLASTIC LIMIT AND PERCENTAGE OF SATURATION. BEARING TESTS ARE MADE ON PLASTIC SOILS WITHOUT SOAKING OR USING A SURCHARGE ON THE SPECIMENS. FOR GRANULAR MATERIALS DESIGN BEARING VALUES ARE DETERMINED FROM TESTS ON SPECIMENS COMPACTED TO AASHO MAXIMUM DENSITY AND SUBJECTED TO FOUR DAYS SOAKING FROM THE BOTTOM. A SURCHARGE IS USED DURING THE SOAKING AND BEARING TESTS. A CURVE WAS DEVELOPED BY PLOTTING THE BEARING VALUES OBTAINED IN THE MODIFIED CALIFORNIA BEARING TESTS DESCRIBED ABOVE AGAINST THE COMBINED THICKNESS OF BASE AND MAT FOUND AT THE TEST POINT IN THE FIELD. BY USE OF DISTINCTIVE SYMBOLS REPRESENTING FAILURE AND NON-FAILURE, IT WAS FOUND THAT THE CURVE COULD BE DRAWN IN SUCH A POSITION AS TO INDICATE MINIMUM THICKNESSES ABOVE WHICH PRACTICALLY NO FAILURE OCCURRED. THIS CURVE AND THE ABOVE DESCRIBED TEST PROCEDURE FORM THE BASIS OF DESIGN OF FLEXIBLE BASES IN MINNESOTA. /AUTHOR/
Supplemental Notes: Vol 26, pp 44-57, 10 FIG, 2 TAB, 4 REF. 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.
Monograph Title: Monograph Accession #: 01490427
Authors: Swanberg, J HHansen, C CEditors: Crum, Roy WBurggraf, FredCarey Jr, William NPublication Date: 1947 (approximate)
Serial:
Highway Research Board Proceedings
Volume: 26 Media Type: Digital/other
TRT Terms: Uncontrolled Terms: Old TRIS Terms: Subject Areas: Geotechnology; Highways; Pavements
Files: TRIS, TRB
Created Date: May 29 1972 12:00AM
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