Tensar Geogrid solution stabilises Thirsk Bypass

Tensar SS30-G geogrid/geotextile composite was laid over the whole roadway and no further remedial action was required.

The A19 Thirsk bypass was originally constructed in the early 1970s, using pavement quality concrete.

Over the years significant moisture ingress into the clay formation via the expansion joints has caused movement in the slabs and the ride quality of the pavement to deteriorate.

The Highways Agency and Autolink Concessionaires (A19) agreed in partnership to jointly fund the reconstruction of the concrete carriageway in bituminous materials providing low noise surfacing.

Colin Thompson, Area Manager at Tensar International, worked with main contractor Cumbrian Industrials to propose Tensar SS30-G geogrid/geotextile composite as an economic and environmentally beneficial solution.

The composite stabilises the sub-base over the clay formation, enables the re-use of the concrete and minimises the requirement for imported aggregate.

Mike O'Grady, site engineer for the project explained: "The project comprised 4km of dual carriageway, running North/South, surfaced with 250mm thick concrete slabs over a clay composite formation".

"The surface was noisy and the ride quality was poor especially around the joints, where water had also infiltrated to some extent." "The concrete was broken out, removed and crushed off-site to DOT Type 1 grading".

"The water infiltration had caused numerous soft spots in the clay but, as we were able to lay the Tensar SS30-G geogrid/geotextile composite over the whole roadway, no further remedial action was required".

"The crushed concrete sub-base was laid and compacted over the geogrid which interlocked with and reinforced the fill, and the underlying geotextile was to ensure no migration of fines up into the sub-base".

"The pavement was finished with a polymer modified, thin surface asphalt coating, which reduces spray and traffic noise".

"Using the Tensar SS30-G reduced the time, aggregate cost and environmental impact of the project, with lower noise and spray".

The project was funded by the Highways Agency and the managing agent, Autolink.

Main contractor: Cumbrian Industrials.

Geogrid laying sub-contractor: Seymour Civil Engineering.

Consultant engineer: Scot Wilson Kirkpatrick.

Managing Agent: Autolink Concessionaires (A19).

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