An experimental study on the compaction and collapsible behaviour of a flood defence embankment fill

With renewed interest in the performance of flood embankments globally, it is important that the performance of fills in conditions similar to 'as-constructed' are scrutinised. The fill material investigated in this study was sampled from flood embankments located along the Bengawan Solo River in East Java, Indonesia. The recurrent history of overtopping and stability issues in these embankments provided the motivation for developing a better understanding of the behaviour of this compacted fill under different loading and wetting conditions. The site investigation revealed that the embankment fill was compacted at low dry densities and that there was local variation in the dry densities determined. A detailed study highlighted that at low compactive efforts this fill material exhibits an irregular double-peak compaction curve, which can be explained by the tendency of this fill to form aggregates on wetting. To cover different plausible operational conditions of these embankments, saturated and unsaturated compression oedometer tests and one-dimensional collapse tests were performed under different initial conditions. Specimens compacted at conditions similar to 'as-constructed' exhibited significant collapse deformation (up to 13.6%) on wetting. Evolution of the microstructure during loading and wetting paths was investigated using MIP and ESEM. A physically-based framework proposed by Romero (2013) was used to explain the changes in the macroscale collapse behaviour observed in the oedometer tests based on the evolution of microporosity. Using this model the evolution of the microporosity with dry density and water content was presented. This microstructural approach could be used as a tool for specifying appropriate compaction conditions for earthworks where fill material is susceptible to volumetric collapse. (C) 2014 Elsevier B.V. All rights reserved.