DISCUSSION OF THE SIGNIFICANCE OF CAP AND BASE RESTRAINT

THE AUTHORS ARE CONGRATULATED ON THE PRESENTATION OF TEST DATA AND FOR THEIR DISCUSSION OF THE EFFECT OF END RESTRAINT IN TRIAXIAL TESTING. MESSRS. HILLIS AND SKERMER HAVE FOUND THAT END RESTRAINT AFFECTS THE TANGENT MODULUS OF ELASTICITY, AND IN MANY CASES THIS HAS AN IMPORTANT BEARING ON THE RESULTS OF STRESS STRAIN ANALYSES SUCH AS THE FINITE ELEMENT METHOD. THE USE OF LUBRICATED END PLATENS PRODUCES A SIGNIFICANT DECREASE IN THE INITIAL TANGENT MODULUS. THE WRITERS HAVE ALSO FOUND AS THE AUTHORS DID THAT SAMPLES TESTED USING STANDARD END PLATENS DILATE MORE THAN THOSE TESTED USING LUBRICATED END PLATENS. THE WRITERS HAVE FOUND IT PARTICULARLY IMPORTANT TO ACHIEVE HOMOGENEITY OF SAMPLE COMPACTION IN TESTING REMOULDED SAMPLES USING LUBRICATED END PLATENS. THEY HAVE ACHIEVED A CONSIDERABLE IMPROVEMENT BY PREPARING SAMPLES LONGER THAN NECESSARY, SCALPING OFF THE TOP AND BOTTOM A FEW INCHES, AND TESTING ONLY THE CENTER SECTION OF THE SAMPLE. CHANGES IN MOISTURE CONTENT ARE DISCUSSED ON THE UNDRAINED STRENGTH OF MANY SOILS. MESSRS. ROWE AND BARDEN REPORT USING A MINIMUM SIZE OF 4-IN. DIAMETER SAMPLES FOR RESEARCH IN SANDS AND REMOULDED CLAYS WHERE THE UNIFORMITY OF THE SAMPLE AND THE ACCURACY OF MEASUREMENT OF ITS PROPERTIES IS ENHANCED. IN THE CASE OF UNDRAINED TESTS ON CLAYS THE AUTHORS NOTE THAT THE PORE PRESSURE EQUILIBRIUM IS REACHED QUICKER WITH FREE ENDS. THIS SEEMS OF CONSIDERABLE FINANCIAL IMPORTANCE TO THE WRITERS, NOT ONLY IN THE INDIRECT COST OF DELAY IN THE PREPARATION OF THE SITE REPORT. THE LENGTH OF THE ASSOCIATED MEAN DRAINAGE PATH IS DISCUSSED IN CONNECTION WITH EQUALIZATION THAT MAY BE ACHIEVED. ANY REDUCTION IN EFFICIENCY OF DRAINAGE IN A CONSOLIDATED UNDRAINED TEST ONLY LEADS TO A HIGHER BACK PRESSURE AT THE START OF THE UNDRAINED COMPRESSION AND THIS CAN BE ALLOWED FOR IN THE CHOICE OF THE CELL PRESSURE. NO ACCEPTABLE STRESS-STRAIN ANALYSIS OF PLANE STRAIN PROBLEMS IS AVAILABLE WHICH TAKES INTO ACCOUNT PROGRESSIVE FAILURE. REFERENCES: THE SIGNIFICANCE OF CAP AND BASE RESTRAINT, JAMES M. DUNCAN AND PETER DUNLOP, ASCE (PROC. PAPER 5768), JANUARY, 1968.

  • Supplemental Notes:
    • Vol 95, Smi, PP 436-441, 2 FIG, 1 REF, 1 APP
  • Corporate Authors:

    N/A

    ,   United States 
  • Authors:
    • Hillis, S F
    • Skermer, N A
    • ROWE, P W
    • Barden, L
  • Publication Date: 0

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  • Accession Number: 00229695
  • Record Type: Publication
  • Report/Paper Numbers: No SM5, Proc Paper 490
  • Files: TRIS
  • Created Date: Aug 15 2004 2:39AM