Highways Retaining Wall
Embankment Retention, Webwall, Dunsop Road, Clitheroe, UK
|Client:||Lancashire County Council|
|Contractor:||Lancashire County Engineering|
|Consultant:||Lancashire Highways Department|
|Product:||Webwall Geocell 250/500|
|Quantity||135m2 of retained face|
|Benefits:||- Easy to place and fill by hand|
- Green natural finish
- Containment for lightweight aggregate
Dunsop Road is part of the Queen’s Estate East Lancashire. The road runs through the popular Forest of Bowland an Area Of Outstanding Beauty. Climbing up the steep embankment above the River Hodder the road suffered extensive damage. This was due to heavy rainfall runoff from the meadows above which closed the road for several months. The embankment had suffered a translational slip cutting into the road edge which was then exacerbated by the runoff water and subsequent erosion.
Due to the steep slopes and limited access it was vital that a solution was found which would be easy to install and would not require large amounts of heavy machinery. The ground was heavily saturated and any excavated fill would not be suitable for re-use. As the road is an environmentally sensitive area there was a strong precedent to try to find a green and as natural finish as possible. With the continuing heavy rains it was not safe to try further works until the spring and the road is a key spine road for visitors and the local residents. This put pressure on the speed of the solution as closing the road had serious consequences as alternative routes meant long detours. A retaining solution was required which would not overload the steep embankment create a green finish and be easy and quick to install without heavy machinery.
Firstly the fill had to be replaced with as light a fill as possible to reduce bearing pressure and to prevent further slips. An expanded clay ceramic bead like product with up to 85% less bulk density and 75% reduction in horizontal pressure on earth structures was selected. This however had to be contained and compacted. The lightweight ABG Webwall geceoll was chosen for the retaining wall as it contained the fill locally, was easy to install and compact using light machinery. The cellular system is opened and pinned to the shape of the slope to blend with the rest of the embankment. Webwall geocell front facing panels were over filled local topsoil and seeded with indigenous seed mixes providing a green finish blending in completely with its surroundings.
As the product is manufactured and supplied in strips which are then pinned into place the installation time is dramatically reduced in comparison with other methods, this allowed down time to be minimised and contributed to the fact that the road reopened 4 days ahead of schedule.
Webwall pinned into place in layers easily filled with the light weight aggregate and compacted by hand. This creates a stable reinforced retaining structure supporting the road with minimal load on the embankment.
The ABG Service
ABG provided full technical support, including design and installation advice.
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