COMPLEX NATURE OF ROCK FACE REQUIRES SPECIALIST SOLUTION
Maccaferri, specialists in retaining structures, soil reinforcement and erosion protection, has recently supplied 4,000 square metres of its Steelgrid woven geocomposite steel mesh to Network Rail as part of a major programme of works to the Highland Line. The mesh was required to stabilise the rock face in the area of Kyle of Lochalsh at the western end of the line which runs from Inverness on the east coast.
The job was made more complex by the composition of the rock face. Formed from schist, a fissile metamorphic sediment, the slope features both convex and concave aspects with loose clumps of boulders. A rockfall netting which combined high strength with the flexibility to conform to the rock face was specified. Maccaferri’s Steelgrid manufactured from double twisted galvanised wire mesh and reinforced with high tensile steel cables with a nominal tensile strength of 1770N/mm2 met the specification.
The work was completed over a four week period from 17th February to 19th March, during which time train services were suspended from Strathcarron to Kyle of Lochalsh. As part of a larger programme, which also included strengthening the sea defences, the work involved cutting back the rock face and the installation of Steelgrid and rock bolts to stabilise the slope.
Protected by international patents, Steelgrid is designed for use in applications which demand greater strength than that offered by traditional rockfall protection netting. Available with the option of mono (Steelgrid M) or bi-oriented (Steelgrid B) cable reinforcement, the vertical cables are used in place of conventional selvedge wires and are also inserted longitudinally within the woven mesh at pre-determined intervals.
For bi-oriented applications requiring structural strength in two dimensions, transverse cables are inserted through the twists within the mesh and secured around the edge cables with aluminium suaged connections.
In addition to rockfall applications, Steelgrid is also appropriate for use with soil nails in slope stabilisation applications and can be used with a range of steel plate anchorage systems. It was developed by Maccaferri in Italy and has already been used in a number of applications across Europe and the USA.
Steelgrid is supplied in rolls with a standard three metre width and a length of 25 or 50 metres. Currently there are four standard specifications: mono oriented Steelgrid M with a longitudinal rope spacing of 1.5 metres and bi oriented Steelgrid B with three alternative rope spacings, 1.5 x 1.5 metres, 3 x 3 metres and 1.5 longitudinal x 2 metre transverse cables. In addition, the location of cables can be customised to meet individual strength specifications, avoiding any redundancy or over-specification in materials.
The UK arm of the Italian-based Maccaferri Industrial Group, Maccaferri Ltd specialises in gabions, geotextiles, geogrids and geomats. In addition to a full range of products for retaining structures, soil reinforcement and erosion protection, the company offers design support, technical advice and,where appropriate, indemnified design and construction services.