Contents
Background
Design/ Check: DCC Engineering Design Group (EDG)
Contract: NEC 3 Option B
Project Management/ Supervision: EDG
Works Duration: 8 months (2 phases of 4 months)
Year completed: 2015
Works value: £670,000
Location: B3227 Black Cat, Bampton
A 360m long section of the B3227 is cut into a very steep hillside, the existing road was supported on a combination of
steep ground, drystone walls and gabion retaining walls. The road support was experiencing landslips and failing old
structures, with sections of the road suffering from collapse.
A new retaining wall scheme was required to address the stability issues and provide a new and compliant road safety
barrier to protect the steep drop to the A396 below.
What were the options?
Various forms of retaining walls including reinforced concrete cantilever walls, mass concrete walls and anchored piled
walls were considered. However, due to the considerable length of works a solution that was relatively quick to construct
and cost effective was required.
A mass concrete retaining wall formed from bespoke precast units and insitu concrete was adopted. The precast units
were designed to be stacked and infilled, these were cast offsite. The use of precast units removed the need for complex
edge shuttering and support, the precast units were designed to allow scaffolding to be supported directly from them,
negating support from the steep hillside.
The retaining wall varied from 3.0 to 4.0m in height and due to the shape of the precast units the curved nature of the road
could be easily accommodated.
Who was involved?
An Engineer and a Technician from one of DCC’s EDG bridges and structures design teams undertook the project
management, design, detailing, procurement and site supervision.