Geotechnical specifications for sustainable transport infrastructure [published as: Sustainable earthworks specifications for transport infrastructure]

The specification of the materials and methods used in earthworks and foundations for highways, railways and airfield runways can be approached in several ways. However, in part due to the sustainability agenda there is a need to use specifications that make best use of material properties, and a performance-based specification may be considered the best way to facilitate this. The advantages and disadvantages of the different specification approaches is described and discussed in this paper. The functional requirements of a performance-based specification for UK highway foundations are considered. The (recently researched) performance-based specification is explained, demonstrating the steps to its development, determination of the engineering requirements, suitable target values and the potential construction-related implications. It is shown that performance-based specifications offer the advantage of better incorporation of the principles that underpin sustainable construction but also require a fuller understanding of material behavior for their development and implementation. However, contractual issues and implications for construction need to be carefully considered to allow a full performance-based approach to be successfully adopted. It is considered in the UK that a staged implementation of a performance specification is necessary to permit the gaining of experience of both the process and the field measurement methods, some of which are relatively novel, and to reduce the risk of contractual disputes or potential failures and thus a negative reaction from the industry.