HIGHWAY CONSTRUCTION PROBLEMS INVOLVING PLASTIC VOLCANIC ASH

ALONG THE EASTERN SHORES OF THE ISLAND OF HAWAII ARE SOILS DERIVED BY WEATHERING OF VOLCANIC ASH UNDER CONDITIONS OF CONTINUOUS MOISTURE. THIS HAS RESULTED IN A VERY PLASTIC TYPE OF SOIL WITH NATURAL MOISTURE CONTENT GENERALLY CLOSE TO 200 PERCENT. THE CONTAINED MOISTURE IS NOT FREE WATER AND HENCE CANNOT BE DRAINED. DUE TO THE ALMOST CONTINUOUS RAINFALL, THE DEEPER LAYERS MAINTAIN THEIR HIGH MOISTURE CONTENT. THE SURFACE LAYERS, MEASURING 6 TO 18 IN. THICK, ARE SUBJECT TO PARTIAL DRYING. DRYING EFFECTS AN IRREVERSIBLE CHANGE IN THE SOIL FROM PLASTIC TO RELATIVELY NON-PLASTIC. THUS PASSENGER CARS AND LIGHT TRUCKS CAN TRAVEL OVER THE TOPSOIL. ON THE OTHER HAND, THE UNDER SOIL, DUE TO ITS HIGH PLASTICITY, WILL NOT SUPPORT RUBBER-TIRED TRAFFIC. EQUIPMENT WITH CATERPILLAR TREAD, HOWEVER, CAN BE USED SUCCESSFULLY WITHIN CERTAIN LIMITATIONS. THESE LIMITATIONS STEM FROM THE FACT THAT THE UNDERSOIL IS THIXOTROPIC, SO ANY UNDUE WORKING OR MANIPULATION OF THE SOIL CAUSES IT TO LOSE ALL STABILITY WITH RESULTANT BOGGING DOWN OF EQUIPMENT AND SLIDING OF EMBANKMENT SLOPES. EXCAVATION CAN BE HANDLED EXPEDITIOUSLY BY USING EQUIPMENT SUCH AS A DRAGLINE, TAKING THE MATERIAL OUT IN ONE LIFT AS CLOSE AS POSSIBLE TO REQUIRED GRADE. THE FRESHLY EXPOSED UNDERSOIL MUST BE QUICKLY COVERED WITH 18 IN. OF SELECT ROCKY MATERIAL TO FORM A TEMPORARY SURFACE (WHICH LATER BECOMES THE SUB-BASE) FOR TRUCKS HAULING AWAY THE EXCAVATED MATERIAL. CARRYALLS FITTED WITH ATHEE TRACKS HAVE ALSO PROVEN SUCCESSFUL UNDER CERTAIN CONDITIONS. EMBANKMENTS ARE BEST CONSTRUCTED IN ALTERNATE LAYERS OF 5 FT. OF ASH AND 18 IN. OF STABLE ROCKY MATERIAL. THE LATTER SERVES AS A TEMPORARY STABLE SURFACE OVER WHICH EQUIPMENT SUCH AS TRUCKS AND TRAC-FITTED CARRYALLS CAN BRING UP MATERIAL. COMPACTION IS DEPENDENT UPON CONSTRUCTION TRAFFIC ENTIRELY. THIS LAYER METHOD ACHIEVES SATISFACTORY COMPACTION WITHOUT DANGER OF TOO INTENSIVE WORKING OF THE MATERIAL. END-DUMP METHODS CAN BE USED FOR RELATIVELY LOW AND SHORT EMBANKMENTS. FOR LONG EMBANKMENTS AND FOR HEIGHTS OVER 15 FT., END-DUMP METHODS RESULT IN TOO INTENSIVE WORKING OF THE MATERIAL WITH CONSEQUENT DANGER OF SLIDES. /AUTHOR/

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  • Supplemental Notes:
    • No 44, pp 1-10, 5 FIG, 7 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
  • Authors:
    • HIRASHIMA, K B
  • Publication Date: 1951

Media Info

  • Media Type: Print
  • Pagination: pp 1-10
  • Monograph Title: Volcanic ash and laterite soils in highway construction
  • Serial:

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Filing Info

  • Accession Number: 00215110
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Apr 28 1994 12:00AM