A review of geotechnical specifications for sustainable 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, due to the sustainability agenda there is a need to use specifications that make best use of material properties. The advantages and disadvantages of different specification approaches are described and discussed in this paper and a performance-based specification is considered the best way to facilitate sustainability. The functional requirements of a recently researched performance-based specification for UK highway foundations 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 behaviour 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.