Membrane Penetration Effects in Triaxial Testing

Abstract

Membrane penetration effects in drained and undrained tests are discussed. A qualitative analysis is performed to find which factors influence the membrane penetration and, at least approximately, to what extent. It is shown that apparent volumetric strain due merely to membrane penetration decreases linearly with increasing sample diameter. The factor of major influence is the grain size but confining pressure, rigidity and thickness of membrane play a non‐negligible role. A method to correct the measured values of pore pressure in undrained tests is proposed. It is shown that the correction factor depends on the volumetric stiffness of the sample which is not a constant but depends markedly on the state of stress.