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Chalk cuttings on CTRL saved from barren future

STEEP CHALK cuttings on the Channel Tunnel Rail Link should soon lose their stark appearance thanks to soil containment and reinforcement work.

MMG Civil Engineering's Erosaweb and Erosamat products are being used to help establish vegetation on the cuttings through the North Downs in Kent. The work is being carried out as part of Contract 420 on the CTRL for main contractor Hochtief/Norwest Holst JV.

The 350m long, 12m deep cuttings were dug through structurally sound chalk at up to 50infinity. Since the steep faces were unable to support any plant growth, the cuttings would have had a barren appearance.

The contractor needed to create an environment that would allow vegetation to establish over the chalk surface.

This was achieved using an Erosaweb honeycomb soil confinement system laid on top of the chalk face and secured with mild steel J pins. The system was installed by subcontractor Land & Water Services.

The Erosaweb cells provide sufficient soil containment to support good moisture retention for roots, allowing the ongoing establishment of grass cover during dry periods.

To protect the gentler upper cutting slopes from erosion and to provide permanent root zone reinforcement for the vegetation, 150mm of topsoil was placed on the chalk with 20mm thick Erosamat installed on the surface. The topsoil was then hydroseeded with a drought-resistant seed mixture.

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