Phi Group Retaining Walls, Soil Nailing and Reinforced Soil

Phi Group is a leading retaining solution provider in the UK, manufacturing, supplying and building retaining structures including timber crib and concrete crib retaining walls, soil nailing, soil panels, modular block, reinforced earth systems,
concrete panel faced reinforced soil and planted / grassed reinforced soil slopes.

The service Phi Group offers includes the design, supply and construction of retaining structures by in-house chartered engineers and is backed up by full indemnity insurance.

Phi Group’s directly employed, experienced construction teams operate nationwide, completing the total design, supply and build package, thus affording optimum peace of mind and minimum risk to client and contractor alike.

SOIL NAIL FACING

Phi Group was responsible for the design, supply and construction of soil nailed slopes for the new slip roads into Stansted Airport from the M11. The site geology consisted of a thin layer of terrace gravels over London clay, which lent itself to
the use of the soil nailing technique of slope stabilisation.

The client required a vegetated finish to the soil nailed face with slope angles varying between 26° to 55°, and an adequate thickness of topsoil had to be provided to enable vegetation to successfully establish.

For the steep slopes, a geosynthetic, cellular matting was installed to provide full depth support to the topsoil. For the shallower slopes, where the topsoil is relatively self supporting, a geosynthetic, erosion control matting was pinned to the
slope.

REINFORCED SOIL SYSTEMS

A steep faced retaining solution to a new roundabout approach road was required as part of the new Terminal 5 infrastructure at Heathrow. The client required an even change in face angle over the length of the roundabout slopes, in combination with a
high spec vegetated finish, aided by an irrigation scheme to help establishment in the first few years.

Phi Group supplied and installed a fully vegetated slope, with face angles varying between 26º and 64º, over slip road lengths of approximately 140m and reaching maximum heights of 9m.

The Textomur system utilised site won terrace gravel fill and geogrid reinforcement. The reinforced soil slopes were constructed in stages with other structures including an arched road portal, river culverts, highway services and safety barriers.

CONCRETE PANELS AND TIMBER CRIB WALLS

A 14m high, reinforced soil wall was designed and installed to support an access road into the Queen Elizabeth Distribution Centre at Purfleet.

This solution, offered by Phi Group, cut two thirds off the cost of the original proposal for a contiguous bored piled wall. Smooth galvanised steel strips, 11m long, used to reinforce the granular fill material, were bolted to steel lugs cast into
the back of the concrete panels.

One of Phi Group’s largest ever crib walling contracts in the UK was at the South Benwell Regeneration project in Newcastle-upon-Tyne. A 5,738m² timber crib wall was constructed.

The walls are founded on both sandstone and silty clay, interrupted by a number of coal seam outcrops. In certain locations, the standard footings were upgraded to form fully spanning, Reinforced Concrete (RC) slabs over areas of potential mine
working subsidence. Loading on walls varied from pedestrian traffic to far more onerous vehicular loads, where the crib walls directly retained the site access road.

Please also see Railway Technology – Phi Group – Retaining Structures and Reinforced Earth Systems