Maccaferri’s Geogrid Systems Support Elevated Railway Viaducts in Reading

Maccaferri’s ParaLink® and MacRes® systems were used to support one of the longest railway viaducts in the UK.

The ParaLink® geogrid was used as basal reinforcement, whereas the MacRes® system with ParaWeb® geostrips formed reinforced soil walls with a vertical concrete panel fascia.

To ease the bottleneck which had troubled the railway system around Reading for years, a 2,000m-long railway viaduct was designed, with an investment of around £45m. This would carry one railway over the another, enabling both lines to operate at the same time without interruption, relieving the bottleneck.

Such a viaduct required long approach ramps to be constructed to raise the line by approximately 6m. Also, working within 15m of the existing operational rail line meant that conventional earthwork ramps were not feasible as there was insufficient space.

Working with the main contractor Balfour Beatty, Maccaferri UK designed reinforced soil retaining walls, compliant with the tender design proposed by Atkins, the project consulting engineers working for client Network Rail.

To fit the tight space constraints, in the tender design Atkins had conceived the solution of a vertical, reinforced soil walls (RSW), with discrete concrete fascia panels on one side of the ramps with a 1:2 slope on the other. Additionally, to provide a suitable foundation for the highly loaded ramps (and RSW structures), ground improvement was deemed necessary, owing to the variable nature of the existing soils.

To this end, Atkins proposed vibro concrete columns (VCCs), with a geogrid-reinforced Load Transfer Platform (LTP). Detailed design of the platform was carried out by Maccaferri in conjunction with specialist consulting engineers Coffey Geotechnics, using the ultra-high strength geosynthetic geogrid ParaLink® as the geosynthetic reinforced LTP.

Under the direction of Maccaferri UK, Coffey also designed the reinforced soil ramp walls, by using the concrete panel vertical faced, reinforced soil system MacRes®. Soil reinforcement in this system is provided by ParaWeb® geostrips, one of the most tried and tested soil reinforcement systems.

Completed in January 2015, the Reading infrastructure is believed to be one of the longest concrete panel faced railway viaducts in the UK supporting live tracks.

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