NEW OEDOMETER AND NEW TRIAXIAL APPARATUS FOR FIRM SOILS; STRENGTH AND DEFORMATION PROPERTIES OF PRECONSOLIDATED MORAINE CLAY; TIME DEPENDENCE OF SETTLEMENTS

AN OEDEMETER IS DESIGNED TO MEASURE THE VERTICAL DEFORMATIONS OF THE SAMPLE AND TO ELIMINATE ERRORS OF VERTICAL DEFORMATION IN THE APPARATUS ITSELF. THE APPARATUS IS CONSTRUCTED OF ONE RIGID UNIT TO AVOID DEFORMATIONS WITH THE DIAL GAUGES MEASURING DIRECTLY AT THE UPPER PRESSURE HEAD. THE OEDOMETER RING IS VERY THICK AND HIGH VERTICAL PRESSURES CAN BE APPLIED WITHOUT CAUSING SIGNIFICANT VERTICAL DEFORMATIONS THROUGH HORIZONTAL EXPANSION OF THE RING. IN OEDOMETER TESTS ON MORAINE THE BEDDING EFFECT CAN BE REDUCED BY CASTING OUT THE GYPSUM BETWEEN SAMPLE AND PRESSURE HEADS. WHEN MAKING TESTS ON SAND, IT IS IMPOSSIBLE TO CAST OUT WITH GYPSUM BUT CONSISTENT CALIBRATION CURVES CAN BE MADE. A TRIAXIAL APPARATUS IS DESCRIBED IN WHICH THE CYLINDRICAL SOIL SPECIMEN IS PLACED BETWEEN TWO PRESSURE HEADS AND SURROUNDED BY A THIN RUBBER MEMBRANE SEPARATING THE PORE WATER AND THE WATER IN THE CELL. WHEN PERFORMING TRIAXIAL TESTS IN THE LABORATORY TO OBTAIN STRESS OR STRAIN PARAMETERS, IT IS EMPHASIZED THAT IT IS IMPORTANT TO HAVE A UNIFORM STRESS AND STRAIN DISTRIBUTION. THIS IS THE CASE IN OEDOMETERS, BUT IN TRIAXIAL TESTING IT IS NECESSARY TO CHANGE THE HEIGHT OF THE SAMPLE FROM TWICE THE DIAMETER TO THE SAME AS THE DIAMETER AND TO USE SMOOTH PRESSURE HEADS. SEVERAL MORAINE CLAYS WERE INVESTIGATED. THE MOST SUITABLE SETTLEMENT ANALYSIS WAS FOUND TO INCLUDE ONLY THE INITIAL TANGENT OF RELOADING CURVES ON THE OEDOMETER TESTS. CONSOLIDATION TIME WAS DETERMINED FOR CIRCULAR FOOTINGS ON THE SURFACE OF PRECONSOLIDATED MORAINE CLAY. THE DETERMINATION OF THE COEFFICIENT OF PERMEABILITY IN THE LABORATORY WAS FOUND TO INVOLVE SOME SOURCES OF ERROR. PERMEABILITY TESTS ON MORAINE CLAY SHOW THAT THE COEFFICIENT OF PERMEABILITY IS INDEPENDENT OF PORE WATER FLOW. CALCULATION ON THE BASIS OF THE THEORY OF ELASTICITY CAN BE CARRIED OUT IF THE BOUNDARY CONDITIONS ARE KNOWN. TWO IMPORTANT DIFFERENCES ARE POINTED OUT BETWEEN THE THEORY OF ELASTICITY AND THE BEHAVIOR OF THE SOIL: (1) THE COEFFICIENT OF ELASTICITY INCREASES WITH DEPTH, AND (2) PRECONSOLIDATED CLAYS EXPAND UNDER GREAT SHEAR STRESSES. CONSEQUENTLY PORE WATER SUCTION EXISTS IN THAT PART OF THE SOIL WHICH ACCORDING TO THEORY SHOULD HAVE MAXIMUM EXCESS PORE WATER PRESSURE. GOOD AGREEMENT WAS OBTAINED FOR CONSOLIDATION TIME BETWEEN THEORY AND OBSERVATIONS, AS DEMONSTRATED BY SETTLEMENT OBSERVATIONS AND PLATE TESTS.

  • Supplemental Notes:
    • Bull No 27, 60 PP, 84 FIG, 11 TAB, REFS
  • Corporate Authors:

    Danish Geotechnical Institute

    1 Maglebjergvej
    DK-2800 Lyngby,   Denmark 
  • Authors:
    • Jacobsen, M
  • Publication Date: 1910

Subject/Index Terms

Filing Info

  • Accession Number: 00235746
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 26 1970 12:00AM