The Queensland Department of Transport and Main Roads (TMR) earthworks specification, MRTS04 General Earthworks (2023), classifies earth fill into five classes, and this project examined how non-conforming materials might be used when compliant materials are unavailable for road embankments. A review of Australian transport agency practices found no uniform national rules, though commonly assessed properties include particle size distribution, California Bearing Ratio, plasticity index, weighted plasticity index, and linear shrinkage, with requirements typically determined by material location within the embankment, environmental conditions, and performance history. Case reviews of Class A2 material used instead of Class A1 indicate satisfactory short-term performance where vegetation is established, though long-term performance remains unverified, and no current software fully models all variables affecting embankment stability. While cohesionless Class A2 materials offer reasonable strength, they are highly susceptible to erosion on embankment batters; mitigation strategies include reducing pavement crossfall, installing kerbs and batter chutes, flattening slopes, and establishing vegetation, although their effectiveness lacks formal feedback from road authorities. Blending materials to improve performance is possible but often avoided due to cost and time, and ultimately, embankment material management remains dependent on site-specific conditions and material variability.
Download ReportDownload Report
