Embankment Reinforcement with ParaLink

This contract is one of a series to construct a continuous grade separated carriageway along the North Wales coastline to improve the link between Ireland (by way of Holyhead) to the Channel ports. This particular construction provides the approach to an immersed tunnel corssing of the Conwy estuary.

An 8m high embankment to carry the carriageway is founded on soft alluvial estuarine clay overlaid by a layer of refuse material, 1m to 4m thick.

Where the alluvial clay was at its shallowest, after having removed the refuse, Terram 2000 was placed to provide a separation filter layer below a drainage blanket of single sized 37.5mm crushed rock.

Over the deepest clay area a drainage blanket (0.4m) was placed directly onto stripped ground. Vertical band drains were then driven through to a depth of 6-10m with the object of shortening the period for dissipating poor water pressure below the embankment. ParaLink 300S was then placed prior to completing in controlled lifts the remaining 2.2m of drainage stone.

ParaLink, a unidirectional polythene coated high modulus polyester (300 kN/m tensile strength), was introduced to take up the stresses imposed by the settlement of the embankment and thereby even out any differential movements.

Instrumentation has been installed under the embankment to monitor the settlement profile, edge momvements and pore pressures.