Gabion Wall, Three Bridges, Crawley

Ian Marychurch

Ian Marychurch

Business Director

Tel: 01483 310600 Email

Client

Spencer Group, on behalf of VolkerFitzpatrick

Services

  • Third party check of reinforced earth design solutions with gabions
  • Construction Supervision
  • Construction Advice
  • Buildability review on the designer’s solution

CGL was appointed by Spencer Group on behalf of VolkerFitzpatrick rail division, who was responsible for the redevelopment of Three Bridges Rail Depot to advise on the design and construction of a headwall and a retaining wall supporting some 12m of fill over a culverted stream.

The challenging task was to extend the existing platform over a running stream and soft soil which required a reinforced soil​/gabion retaining wall with granular fill.

CGL’s role included validating the original design in combination with the designers to produce a solution that could be built. CGL also investigated the founding conditions to provide detailed recommendations on safe bearing pressures and preparation of the formation.

The stream lay within a strip of alluvium, resulting in the highest point of the wall overlying the weakest ground conditions. Therefore, excavation to competent material was required to support the gabion wall effectively, although this required excavation beneath the stream bed level into the weak alluvium. This presented a difficulty in terms of groundwater ingress into the excavation and the softening of the underlying competent clay. CGL devised a plan to keep the stream flowing and overcome the groundwater issue to enable construction to proceed.

The design and construction issues were overcome and a 12m retaining wall was built from reinforced earth and gabions located either side and above the steam to enable the depot area to be extended.