Affiliation:
1. Department of Civil Engineering, University of Birmingham UK
2. Loughborough University UK
3. The Nottingham Trent University UK
Abstract
The road foundation layers perform several functions both during construction and when the road is in service, for example load-spreading, temporary haul routes, and a base for the overlying construction layers. The critical loading condition is usually directing trafficking where the applied stresses are greatest. The capping and sub-base layers during construction require adequate stiffness and strength to resist these stresses. The current UK specification for road foundations is based on a recipe approach, and, unless permission is granted to use an analytical design, the pavement foundation designs are based entirely on the California Bearing Ratio (CBR) to characterise the subgrade, capping and sub-base materials. Here CBR is used as an index of both material strength and stiffness, although it measures neither directly. Such an approach is potentially inefficient and does not readily facilitate the use of new and marginal materials or alternative design procedures. Recent technical advances in laboratory and in situ testing of pavement foundation materials now allow the performance parameters of stiffness, strength and resistance to permanent deformation to be measured both for design and during construction. This in turn enables a performance-based specification for road foundation layers to be introduced to provide some assurance of the as-constructed quality, and by permitting the use of secondary or recycled aggregates, to contribute to the parallel goal of sustainable construction. This paper sets out an idealised philosophy for a performance-based specification for road foundations, examines the individual elements of the specification in relation to current knowledge and makes recommendations for a phased introduction alongside CBR-based methods.
Subject
Transportation,Civil and Structural Engineering
Cited by
5 articles.
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1. Subgrade and Foundation Dynamic Performance Evaluation by Means of Lightweight Deflectometer Tests;Transportation Research Record: Journal of the Transportation Research Board;2014-01
2. Materials science appraisal for recycling materials in roads;Proceedings of the Institution of Civil Engineers - Construction Materials;2012-10
3. Condition assessment of the surface and buried infrastructure – A proposal for integration;Tunnelling and Underground Space Technology;2012-03
4. Pavement foundation stiffness testing – a new regime;Proceedings of the Institution of Civil Engineers - Transport;2010-08
5. Carbon Dioxide Emissions due to Highway Subgrade Improvements;Transportation Research Record: Journal of the Transportation Research Board;2009-01