Experimental artefacts in undrained triaxial testing

TL;DR

This paper presents a correction method for artefacts caused by drainage system dead volume in undrained triaxial tests, improving the accuracy of thermo-poro-elastic property measurements of saturated porous materials.

Contribution

It introduces a correction technique accounting for drainage system effects and identifies key parameters influencing measurement errors in undrained tests.

Findings

Porosity and drained compressibility significantly affect measurement errors.

The ratio of drainage system volume to sample volume influences artefact magnitude.

The correction method improves the accuracy of undrained thermo-poro-elastic property evaluation.

Abstract

For evaluation of the undrained thermo-poro-elastic properties of saturated porous materials in conventional triaxial cells, it is important to take into account the effect of the dead volume of the drainage system. The compressibility and the thermal expansion of the drainage system along with the dead volume of the fluid filling this system, influence the measured pore pressure and volumetric strain during undrained thermal or mechanical loading in a triaxial cell. A correction method is presented in this paper to correct these effects during an undrained isotropic compression test or an undrained heating test. A parametric study has demonstrated that the porosity and the drained compressibility of the tested material and the ratio of the vol-ume of the drainage system to the one of the tested sample are the key parameters which influence the most the error induced on the measurements by the drainage system.