Corrections for Strength Test Data

The loads carried by piston friction, rubber membranes, and filter paper drains may have a significant effect on the axial stress in triaxial test specimens. In plane strain tests, friction between the membrane and the plates used to enforce plane strain deformation also influences the axial stress in the test specimens. Failure to correct for these loads results in an overestimate of the axial stress in the test specimens and influences the values of the consolidation pressure, the strength, the strength parameters, the pore pressure parameter, A, and the effective principal stress ratio. Whether test results are to be used in research investigations or for practical purposes, it is desirable to make appropriate corrections to the test data. Techniques for determining values for the various corrections are discussed, and examples of the corrections are given for both triaxial and plane strain tests.