Constraints in using site-won calcareous clayey silt (loam) as fill materials

BSI recently published the revised BS 6031, to include compliance with Eurocode 7. This placed emphasis on fill classification and compaction specifications, while setting the Specification for Highway Works (SHW) 600 series as the default approach for earthworks in the UK. The revised BS 6031 (and earlier documents such as the 2001 manual of BRE Centre for Ground Engineering and Remediation) lack in explaining long-term ground movements in compacted earthworks, particularly when arisings from nearby cuttings are used as fill materials. Unexplained settlements include sudden and long-term subsidence particularly in transient loading environments, when fills are built from sand/silts with small clay inclusions, as well as seasonal subsidence in fills with <20% carbonates. This paper examines some of these limitations through revisiting our recent research, including a recent experimental work. From this paper, specifications can be developed for building fills with site-won materials with an impact on carbon footprint, haulage and maintenance costs.