Software aids geogrid pavement design

Spectra M-E draws on data gathered by Tensar from testing and trials using its Triax geogrid over the last 30 years.

“Spectra M-E is unique because, for the first time, engineers can use a mechanistic-empirical (M-E) approach to analyse and predict the service life performance of a pavement when Tensar Triax geogrids are incorporated in unbound granular layers,” explained Tensar vice president global product management and technology Tim Oliver.

A granular layer stabilised with a geogrid acts as a composite due to the interlocking mechanism and particle confinement that develops. Mechanical stabilisation can provide more effective support for the entire pavement than aggregates alone.

“Empirical methods use stabilisation factors to assess the benefits of incorporating Triax, which can help reduce pavement thickness, extend service life or a combination of the two,” Oliver said. “The final design can then be assessed for life-cycle costs, including the cost of construction, materials and environmental impact – to ensure the optimal design has been identified.

“M-E analysis uses engineering principles to model stresses and strains in pavement layers caused by traffic loads – the mechanistic part, based upon site-specific conditions, such as founding layers, pavement materials and climate. The performance over time is then modelled, based upon the observed behaviour of pavements from field observation and accelerated testing - the empirical part.

“This iterative process allows engineers to optimise their design to meet a project’s specific performance criteria, over the lifetime of the road, much faster and more accurately,” Oliver explained. “However, up until now, it has not been possible to model the positive effect of stabilisation geogrids.”

According to Oliver, the wealth of empirical data on fatigue, rutting and shearing of road pavements used within the software allows engineers using the program to see the performance benefits of using Triax in their designs.