The lateral swelling pressure on the volumetric behaviour of natural expansive soil deposits

Abstract

For swelling soil volume changes are a function of state variable changes. Usually the most appropiate soil test used to simulate vertical displacements under a building constructed on expansive soil is the oedometer test, with vertical deformations allowed and deformations in the lateral direction prevented. In this paper, the volume change behaviour of the Madrid clay is reported. It was investigated by controlled wetting of undisturbed samples, subjected to constant vertical pressure and decreasing the sample’s matrix suction, by means of a Cuellar’s controlled suction oedometer. Lateral swelling pressure measurements were made using this apparatus. This null type device allows the modelling of changes in season or climate in the laboratory. The swelling test was performed considering that in situ, when water ingresses beneath a building, not only the soil suction changes, but the lateral pressure changes also. Therefore, this paper describes the importyance of predicting soil swell using the mean net stress, instead of the vertical net stress alone, as is usually the case.