A Critical Assessment of Membrane Penetration in the Triaxial Test

Fundamental assumptions necessary for assessment of volume change because of membrane penetration in triaxial tests on granular soils, by methods that use dummy rod inclusions or assume isotropic behavior of sand in loading, have been critically examined and shown to be invalid. Reliable estimates of membrane effects are essential in the development of constitutive models of soil behavior. Alternative methods, which do not violate any critical assumptions, are proposed for estimating membrane penetration and supported by experimental evidence.