PHOTOELASTIC AND FINITE ELEMENT ANALYSIS OF EMBANKMENTS CONSTRUCTED OVER SOFT SOILS

STRESSES AND DISPLACEMENTS WERE DETERMINED EXPERIMENTALLY AND NUMERICALLY FOR MODEL EMBANKMENTS THAT UNDERWENT LARGE DEFLECTIONS WHEN CONSTRUCTED OVER MODELS OF TRENCHED AND UNTRENCHED SOFT ORGANIC SOILS. IN THE EXPERIMENTAL PHASE OF THE STUDY, GRID AND PHOTOELASTIC METHODS WERE USED TO DETERMINE DEFORMATIONS AND STRESSES IN THE MODEL SOIL, WHICH CONSISTED OF A SOFT GELATIN MIX WITH AN EMBEDDED INK GRID. A GELATIN SLAB, WHICH MODELED A CROSS SECTION OF THE SOIL SUPPORTING AN EMBANKMENT, WAS FORMED IN A TANK WITH GLASS SIDES. MODEL EMBANKMENTS WERE PLACED IN THE TANK ON THE GELATIN, AND RESULTING GRID DEFORMATIONS AND PHOTOELASTIC FRINGES IN THE GELATIN WERE PHOTOGRAPHED. EXPERIMENTAL AND NUMERICAL (FINITE ELEMENT) RESULTS FOR MAXIMUM NORMAL AND SHEARING STRESS ALONG THE CENTERLINE BENEATH THE EMBANKMENTS WERE COMPARED WITH RESULTS OBTAINED BY CLASSICAL LINEAR ELASTICITY. FOR EMBANKMENTS UNDERGOING LARGE DEFORMATIONS, WHERE ANALYSIS BY THE CLASSICAL THEORY USING SMALL DEFORMATION RESTRICTIONS AND SUPERPOSITION PRINCIPLES IS SUSPECT, IT WAS FOUND THAT THE STRESS VALUES WERE BOUNDED ABOVE BY THE CLASSICAL SOLUTION IN THE CASE OF MAXIMUM SHEAR STRESS AND WERE VERY CLOSE TO THOSE PREDICTED BY THE CLASSICAL SOLUTION IN THE CASE OF NORMAL STRESS. IT IS CONCLUDED THAT THE DESIGNER IS CONSERVATIVE IN USING THE CLASSIC BOUSSINESQ APPROACH IN PREDICTING BOTH MAXIMUM SHEAR STRESS AND MAXIMUM VERTICAL NORMAL STRESS ALONG THE CENTERLINE AND BENEATH AN EMBANKMENT UNDERGOING LARGE DEFORMATIONS. WHERE TRENCHING IS USED, NEGATIVE (UPWARD) AS WELL AS POSITIVE (DOWNWARD) DISPLACEMENTS SHOULD BE TAKEN INTO ACCOUNT IN ESTIMATING THE AREA OF THE NET CROSS SECTION OF AN EMBANKMENT. TRENCHING IS NOT RECOMMENDED FOR THE PLACEMENT OF EMBANKMENTS ON SOFT FOUNDATIONS UNLESS (A) THE TRENCH IS TO BE USED AS AN ECONOMICAL WATERWAY TO TRANSPORT BULK EMBANKMENT MATERIAL AND EQUIPMENT FOR THE CONSTRUCTION, OR (B) THE TRENCHING OPERATION WILL REMOVE SOFT MATERIAL AND EXPOSE STIFFER LAYERS WITH HIGHER BEARING CAPACITY. UNTRENCHED EMBANKMENT CONFIGURATIONS PRODUCED NO STRESS CONCENTRATIONS BENEATH THE EMBANKMENT. /AUTHOR/

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  • Supplemental Notes:
    • Paper sponsored by Committee on Embankments and Earth Slopes. 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:
    • Thoms, Robert L
    • Arman, Ara
  • Publication Date: 1970

Media Info

  • Media Type: Print
  • Features: Appendices; Figures; References;
  • Pagination: pp 71-86
  • Monograph Title: Landslides; Slope Protection and Stability; Embankment Design and Stability
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00235858
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 8 1971 12:00AM