Fleming Prize Winner: Crag End Landslip, Manchester

16 October, 2017 | 18:00 - 20:00

Works to improve the stability of the road
Works to improve the stability of the road

About this event

Before and after

The Crag End Landslip project comprises the reconstruction of a 300m section of the B6344 near Rothbury for Northumberland County Council. Closed in December 2012 following multiple landslips and failure of an existing retaining wall, triggered by one of the wettest periods on record, the road provides the main link between Rothbury and the principal road network. The slope and River Coquet below the road form a Site of Special Scientific Interest and the land upslope is part of the Cragside Estate owned by the National Trust.

Closure has had a significant socio-economic impact, and as well as being a major inconvenience to residents it affected the main industries in Coquetdale - farming, forestry and tourism. VBA designed and constructed an anchored bored-piled retaining wall to support the road and an innovative passive dewatering system to reduce groundwater pressure. This robust, low maintenance solution ends decades of instability, leaving an engineering legacy for Rothbury.

The client was keen to reopen the road as soon as possible as residents were faced with a substantial detour to access Rothbury. The local economy depends heavily on tourism which had been badly hit by the road closure. VBA has designed and implemented a solution comprising two main elements – a deep dewatering system to reduce the risk of instability by lowering artesian groundwater pressures, and an anchored bored pile retaining wall to support the road in the event of a slip. The team faced numerous challenges including variable ground conditions, high groundwater and difficult access on a constrained site.

This talk will be an extended version of the presentation which was given during the 2016 BGA Fleming Award Competition in London. The judges the judges announced that, based on the team work required to deliver the project safely and the variety of geotechnical solutions needed for the remediation of a difficult geotechnical problem adjacent to an SSSI area, the Crag End Landslip team (consisting of Volker Stevin, Atkins, Northumberland County Council and Keller) was the deserving winner.

The talk will be split into three parts.

Part 1 will give an overview of the project, discussing the geology and hydrogeology, challenges faced during intrusive ground investigations, causes of instability and the landslip mechanism.

Part 2 will cover the technically complex bored pile anchored retaining wall design, provide an overview of the chosen passive dewatering system, and discuss the design challenges faced.

Part 3 will present an overview of construction works.

Contact

For more information, please contact:

Edouardos Karavakis
e: edouardos.karavakis@Arcadis.com

Speakers

Paul Berry (senior geotechnical engineer, Atkins, Newcastle-Upon-Tyne)

Paul is a chartered geologist with over 12 years' experience and manages geotechnical work in Atkins Newcastle office. Paul has experience of the design and analysis of geotechnical structures, including but not limited to; shallow foundations, retaining walls, embankments, cuttings and soil and rock slopes. He also has experience of slope stability analysis, interpretative reporting and detailed geotechnical design for highways construction. Paul supervised the construction works that allowed the B6344 to be re-opened following a major landslip and is currently managing the monitoring phase of the works.

Michael Gavins (chief geotechnical engineer, Atkins, Warrington)

Mick is a chartered civil engineer with 30 years' experience mainly in the geotechnical and structural design of piled foundations, retaining walls, ground anchorages, deep basements, soil nails and slope stabilisation for highway, rail, energy and commercial schemes in the UK and SE Asia. Having worked predominantly for specialist foundation contractors where Mick held the positions of design manager and technical director, he has also managed multidiscipline foundation projects and sites in the UK and Asia.

Mick provides technical lead in Atkins Ground Engineering for foundations and retaining walls on multiple projects. He has been a member of steering committees for British Standard and CIRIA documents and authored chapters of the ICE manual of Geotechnical Engineering and the ICE Specification for Piling and Retaining walls.

Will Davies (Senior Engineer, VolkerStevin)

Will Davies is a senior engineer with over 10 years construction experience. He has worked throughout the UK on various schemes since joining VolkerStevin in 2002. Will has supervised multi-million-pound flood alleviation and coastal defence works and was involved in the team that constructed the award winning £9M Hexham Flood Alleviation Scheme through a combination of rural and residential areas. Will recently supervised the coastal defence works at Colwyn Bay North Wales.

The works involved raising the current level of flood protection and included installing rock armour groynes, steel piling, pre-cast and in-situ concrete walls, ramps and promenade environmental protection and enhancements, and the reinstatement of roads, footpaths and associated services in line with the raised flood protection. Will was the VBA site agent for the Crag End landslip project and played an instrumental role in ensuring the successful delivery of the project on time and within budget.

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