Cordek supplies Tyne Tunnel with Cellcore system

To address the issues of ground uplift, engineers working on the New Tyne Tunnel Crossing have specified Cellcore from Cordek, incorporating expanded polystyrene from Jablite.

The ground uplift was caused by deep excavation on the access road leading to the tunnel.

Expanded polystyrene manufactured by Jablite is supplied to Cordek to produce its patented Cellcore system.

Cellcore is a honeycomb of interlocking expanded polystyrene sections, designed to collapse at a pre-determined load.

It was anticipated that ground uplift could cause a problem due to the deep cut and cast excavations on the access roads to the tunnel.

If this movement is restrained, the huge lateral and uplift forces produced would eventually result in damage to the reinforced concrete slabs above.

Cellcore enables the EPS to compress and deform to accommodate this uplift.

Type CC Cellcore in four grades was used on this project.

The product is available in a standard panel size of 2.44x1.22m, and features a heavy-duty polypropylene top.

On the New Tyne Tunnel, an additional 50mm blinding layer of concrete was used above and below the Cordek heave protection layer.

Cordek's Type CP Cellcore was developed for use beneath suitably reinforced concrete slabs and includes a 50mm thick polystyrene top, protected by a 2mm thick polypropylene sheet that provides a high degree of insulation.

As Cellcore uses EPS, it absorbs expansion, unlike some other anti-heave products, that rely on material degradation, which means the system is immediately effective.

Once the Cellcore panels were laid and the joints sealed, the surface was ready for the next stage of construction on the tunnel.

Water pressure was a potential problem for the engineers due to the proximity to the river, which resulted in excavations beneath the water table.

This meant that a number of Cellcore panels were supplied with drainage apertures.

In addition to its physical properties, expanded polystyrene is easy to handle and compatible with rapid construction techniques.

As part of modern methods of construction, it can be transported to site in the minimum number of loads, producing less waste and with no negative environmental impact.

Expanded polystyrene is HCFC-free and non-toxic.

The material's closed-cell formation inhibits absorption of water and therefore avoids any problems of waterlogging and drainage.

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