THE RELEVANCE OF THE TRIAXIAL TEST TO THE SOLUTION OF STABILITY PROBLEMS

ACTUAL PROPERTIES OF COHESIVE SOILS MEASURED IN THE STANDARD UNDRAINED, CONSOLIDATED-UNDRAINED AND DRAINED TRIAXIAL TESTS ARE APPLIED TO THE SOLUTION OF MORE IMPORTANT CLASSES OF STABILITY PROBLEMS. THE FAILURE CRITERION CHOSEN AND THE SHEAR PARAMETER BY WHICH THEY ARE EXPRESSED ARE THOSE FOUND MOST CONVENIENT AND MOST APPROPRIATE TO THE METHODS OF STABILITY ANALYSIS USED. THE LOGICAL RELATIONSHIP OF THE VARIOUS STANDARD TESTS TO THE DIFFERENT CLASSES OF STABILITY PROBLEMS ARE PRESENTED AND ATTENTION DRAWN TO THE VARIOUS LIMITATIONS OF THE APPARATUS IN WHICH THE TRIAXIAL TEST IS USUALLY PERFORMED. THESE INCLUDE NON-UNIFORMITY OF STRESS AND STRAIN PARTICULARLY AT LARGE DEFORMATIONS, AND THE INABILITY OF THE APPARATUS TO SIMULATE THE CHANGES IN DIRECTION OF THE PRINCIPLE STRESSES WHICH OCCUR IN MANY PRACTICAL PROBLEMS. THE PRINCIPLE OF EFFECTIVE STRESS DISCOVERED BY TERZAGHI AND ITS EXPERIMENTAL INVESTIGATION ARE REVIEWED. IN SLOPE STABILITY PROBLEMS THE INFLUENCE OF PORE PRESSURE ON THE FACT OR OF SAFETY IS CONVENIENTLY EXPRESSED IN TERMS OF THE RATIO OF THE PORE PRESSURE TO THE WEIGHT OF MATERIAL OVERLYING THE POTENTIAL SLIP SURFACE. THE STANDARD TYPES OF TRIAXIAL TESTS, METHODS OF STABILITY ANALYSIS AND APPLICATIONS TO PRACTICAL PROBLEMS ARE DISCUSSED. A REVIEW OF CASE RECORDS PRESENTED INDICATES THAT EFFECTIVE STRESS ANALYSIS IS A GENERALLY VALID METHOD FOR ANALYZING ANY STABILITY PROBLEM AND IS PARTICUARLY VALUABLE IN REVEALING TRENDS IN STABILITY WHICH WOULD NOT BE APPARENT FROM TOTAL STRESS METHODS. HOWEVER, ITS APPLICATION AND PRACTICE IS LIMITED TO CASES WHERE THE PORE PRESSURES ARE KNOWN OR CAN BE ESTIMATED WITH REASONABLE ACCURACY. WHERE A SATURATED CLAY IS LOADED OR UNLOADED AT SUCH A RATE THAT THERE IS NO SIGNIFICANT DISSIPATION OF THE EXCESS PORE PRESSURES SET UP, THE STABILITY CAN BE DETERMINED BY TOTAL STRESS ANALYSIS, USING THE UNDRAINED STRENGTH OBTAINED IN THE LABORATORY OR FROM IN-SITU VANE TESTS. THE TWO METHODS OF STABILITY ANALYSIS REQUIRE THE MEASUREMENT OF THE SHEAR STRENGTH PARAMETERS, EFFECTIVE STRESS FAILURE ENVELOPE AND TOTAL STRESS IN TERMS OF EFFECTIVE STRESS ON ONE HAND AND THE UNDRAINED SHEAR STRENGTH UNDER THE STRESS CONDITIONS OBTAINED IN THE FIELD ON THE OTHER. THE RELIABILITY OF ANY METHOD CAN ULTIMATELY BE CHECKED ONLY BY MAKING THE RELEVANT FIELD MEASUREMENTS WHEN FAILURES OCCUR OR WHEN CONSTRUCTION OPERATIONS ARE LIKELY TO BRING A SOIL MASS NEAR TO LIMITING EQUILIBRIUM.

• Supplemental Notes:
  • No 34, 56 PP, 31 FIG, 6 TAB, 123 REF
• Corporate Authors:

  N/A

  ,   United States 
• Authors:
  • Bishop, A W
  • Bjerrum, L
• Publication Date: 0

Media Info

• Serial:
  • Norwegian Geotechnical Institute Publ
  • Issue Number: 0

Subject/Index Terms

• TRT Terms: Cohesive soils; Deformation; Effective stress; Field tests; Pore pressure; Properties of materials; Safety factors; Shear strength; Shear tests; Slip surfaces; Slope stability; Soils; Stability analysis; Stresses; Structural analysis; Test procedures; Triaxial shear tests; Vane shear tests
• Uncontrolled Terms: Soil deformation; Soil properties; Total stress; Triaxial testing machine
• Old TRIS Terms: Insitu methods
• Subject Areas: Geotechnology; Highways; Materials; Safety and Human Factors;

Filing Info

• Accession Number: 00231454
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 15 2004 2:41AM