On the Interpretation of the Triaxial Test

Synopsis After reviewing the statical and kinematical indeterminancies of the triaxial test, the Paper describes an experimental investigation into the conditions of strain under triaxial compression. Radial and tangential strains are of special interest and these are estimated from the displacements of lead shot measured using an X-ray technique. The observations were made during drained tests on large diameter triaxial samples of medium dense sand in which the end restraint was either at a maximum using rough platens, or at a minimum using lubricated platens. It was found for the material tested that the normal interpretative assumption of equality between the radial and tangential strains is essentially valid for lubricated samples but largely inadmissible for samples tested with rough platens. In the interests of obtaining reliable strain information from the triaxial sample, it is evident that testing techniques employing lubricated platens are considerably preferable to techniques employing rough pl...