Small Strain Behaviour of Compacted Soils in Transport Infrastructure Formations Subjected to Drying and Wetting

Transport infrastructure is linear and often intersects and is comprised of (i.e. geostructures) several soils of differing characteristics i.e. particle size, mineralogy and thus plasticity. Evaluation of these properties, for example by monitoring small strain stiffness, is critical for assessing compacted soil geomechanical behaviour during service. In this paper the influence of drying-wetting is investigated for three compacted soils representative of soils in the UK, including a low plasticity clayey sandy silt, a high plasticity kaolin clay, and a very high plasticity silty clay. The impact of their composition (e.g. clay content and plasticity) on shear wave velocity during a drying-wetting cycle was monitored at selected gravimetric water content levels. As expected, the results show that higher clay activity (A) results in larger variation of shear wave velocity. In addition, soils with a higher Weighted Plastic Index (WPI) also exhibit larger volumetric changes during drying-wetting. Consequently, the results quantitatively capture the influence of the clay content, which shows a significant effect on the variation in seasonal geomechanical performance. These findings can in turn support proactive asset management strategies that enable the identification of areas of the transport network that may be more vulnerable to seasonal changes in water content.