Client: AMEY Plc
The Eastern Corridor Link Road was a major road improvement scheme which upgraded a strategic transport corridor in Plymouth. The section of road improvement extended 8km from the Deep Lane Junction at Plympton into Plymouth city centre. The scheme accommodates increased traffic associated with the new power station and business park at Langage, Plympton and the new town of Sherford.
As Principal Geotechnical Consultant, JGP provided preliminary and detailed geotechnical and contaminated land ground investigations for the whole 8km Eastern Corridor Link Road scheme. JGP also provided options appraisals, geotechnical design services and construction monitoring.
The site investigations crossed a variety of geological formations and ground conditions, from soft alluvial silts to extremely strong Limestone. The ground investigation also informed an options appraisal, which included proposed routes and different construction methods. JGP also provided detailed geotechnical advice and recommendations for the new embankment design.
The New Embankment
The scheme involved the construction of a new section of road along the Plym Estuary. This required a new embankment to be constructed over soft sediments associated with the Estuary. To facilitate safe construction, JGP designed band drainage to dewater the underlying sodt sediments. Remotely monitored piezometers were also installed to allow pore-water pressures and their dissipation to be monitored as the ground consolidated.
JGP also prepared the AIP, designed and monitored the construction of ground retention works to a previously cut slope at the west end of link road scheme in Gdynia Way. The exposed slates had a susceptibility to sliding and needed to be cut back further to facilitate road widening. Temporary works comprised the installation of cased drilled piles to form a contiguous piled retaining wall. The new wall enabled the excavation of the toe of slope and the installation of a permanent anchored reinforced concrete retaining wall. The works were complicated by the presence of a sewer crossing beneath the slope in a heading and another sewer laid in the highway fronting the wall. The design was adapted to take into account these underground services.