Hydro-mechanical characterization of lime-treated and untreated marls used in a motorway embankment

Some embankments on the A10 motorway, in Portugal, were built with marls. A lime treatment was prescribed for the material placed on the shoulders to protect it from the actions of the weather. This zoned profile design solution was a cheaper alternative to giving the embankment a full treatment.Two major concerns emerged during the construction, which motivated the research presented in this paper. The first was the possibility of cracking induced by the different stiffness of the core and treated shoulders, thus providing access of rain water to the core material, which was exactly what the treatment intended to avoid. The second was the difficulty in estimating the amplitude of long-term deformations, which can be expected due to the evolving nature of the marls used.The research program included the instrumentation of a selected embankment and laboratory tests on samples of treated and untreated compacted marls. The instrumentation allowed the measurement of vertical displacements and water content distribution to investigate if long-term displacements would be a concern during operation. The laboratory tests characterized the hydro-mechanical behavior of the material and its changes with the lime treatment. This research also stimulated discussion of some ideas about the expected performance of the embankment during its life cycle.

► An embankment was built with evolving marls and was monitored to confirm long-term behavior. ► Lime treatment improves marls stiffness and strength and treats part of the long term behavior. ► The hydro-mechanical behavior of marls treated with lime and untreated was characterized. ► The results allow learning about the use of lime treatment for marls when employed in embankments. ► The behavior of untraditional materials is scarce in the literature and is missing in design.