Understanding the age and construction quality of embankments used for road and rail infrastructure is critical in the effective management and maintenance of our transport networks, worth £billions to the UK economy. This paper presents for the first time results from full-scale, carefully controlled experiments on a unique model embankment conducted over the 4-year period between 2008 and 2011. It combines point location and spatially distributed measurements of pore water pressures and water content with outputs from hydrological modelling to draw conclusions of significance to both ongoing research in this field and to the asset management practices of infrastructure owners. For researchers, the paper highlights the crucial importance of transient permeability and soil water retention behaviour of fill materials in controlling the magnitude and distribution of pore water pressure in response to climate and weather events. For practitioners, the work demonstrates that there are significant differences in pore water pressure behaviour across the embankment, which is influenced by construction-related issues such as compaction level, aspect and presence of a granular capping material. Permeability was also observed to vary across the embankment both spatially and with depth, being dependent on degree of saturation and macroscale effects, particularly within a ‘near surface zone’. It is proposed that this ‘near surface zone’ has a critical effect on embankment stability and should be the focus of both ongoing scientific research and inspection and monitoring as encompassed by asset management regimes.

Significant advances in unsaturated soils testing have been gained through the development of high suction tensiometers allowing direct measurement of suction beyond 100. kPa. This has allowed the implementation of techniques that measure and control suction directly, where the soil is tested in the same conditions as in nature. Previously, much reliance had been placed on indirect measurements of suction and on control of suction using the axis translation technique. It is argued that this technique should be avoided as the use of an elevated air pressure does not replicate natural conditions. This paper presents advances resulting from the use of high suction tensiometers for laboratory testing and field measurements. It also describes an automated suction control system using the air circulation method that can impose controlled cycles of drying and wetting. © 2012 Elsevier B.V.link_to_subscribed_fulltex

This paper presents a comprehensive experimental investigation on shrinkage and soil-water retention behaviour at macroscale and microscale of four natural Australian soils upon drying and wetting. Both reconstituted and intact states were tested. First, a comprehensive physicochemical characterization of the four soils was performed to provide a complete picture of the mineralogical composition and surface properties as well as different initial structure associated with reconstituted and intact states. Then, macroscale testing was conducted and complemented by microstructural analyses through mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) observations. These provided a comprehensive picture of the microfabric evolution of the soils tested along the drying–wetting path. All the experimental results were discussed in a coupled multi-scale manner.