Prediction of potential vertical swell of expansive soils using a triaxial stress path cell

Preconstruction treatment or the selection and design of a foundation system both rely on accurate estimates of the potential heave of the supporting expansive soil. The majority of volume change testing of expansive soils has been performed under one-dimensional loading conditions in the oedometer. However, due to differences between laboratory test constraints and field conditions, the amount of volume change measured in various oedometer testing methods may differ dramatically from heave observed in the field. This paper presents the results of an experimental investigation in which the feasibility of using a stress path triaxial cell for evaluating the vertical swell of expansive soils under multidimensional loading conditions was examined. Several series of triaxial swell tests were conducted in which the influence of confinement on the predicted vertical swell was evaluated. The results of these tests were compared with the volume changes observed for samples tested under identical initial conditions in the oedometer. The applicability of the triaxial testing technique was further ascertained by predicting surface heaves observed in an instrumented field test. The triaxial swell tests provided reasonable estimates of the measured field heaves in comparison to the oedometer tests which yielded rather conservative predictions.