Membrane Penetration in Triaxial Tests

Volumetric deformations of triaxial specimens of sand measured with a burette are burdened with an error caused by a rubber membrane penetrating into the peripheral voids of the specimen. This effect is of the same order of magnitude as volumetric deformation of the soil skeleton and should be eliminated. To this end, a method has been proposed based on the K0-stress path. Membrane penetration for the particular material has been approximated by logarithmic and hyperbolic curves. The resulting correction considerably surpasses most published expressions because the latter usually do not consider the porosity of specimens.