Steel reinforcement
In the context of Geosystems steel reinforcement comes in the form of steel strips typically used to reinforce the soil in conjunction with concrete face panel systems, or in reinforced soil slopes by the use of woven, polymer coated hexagonal steel meshes.
Steel meshes can be laid on or just below the surface to reinforce soil on slopes or other areas being vegetated. Meshes can also be used with soil nails to spread the load between the nail heads and contain local soil failures. When sprayed concrete is used, steel meshes can be laid to provide reinforcement and an adhesion surface.
Rock fall control nets are usually made of double twist steel wire netting, fastened at the top of the rock slope and left hanging under its own weight to a bench or the base of the cuttings where any loose rock can accumulate. If the horizontal movement of the rock fall needs to be controlled, the net is loosely anchored with horizontal straps, dowels or tightly wrapped around the slope to prevent any fall of material.
Steel meshes provide a good containment system for very unstable and irregular rock slopes that cannot be rock-bolted. Steel mesh and nets require some form of protection from corrosion, hence the steel wire is galvanised and/or polymer or zinc coated.
In reinforced soil applications, arrays of steel strips are anchored or bolted to concrete facing elements and installed progressively on compacted layers during backfilling to provide reinforcement through resistance to horizontal shear. As horizontal load develops on the wall due to the compaction process and the increasing soil overburden as the wall is constructed, tensions are generated in the reinforcing strips which stabilise the structure.
Care should be taken when choosing metal elements for use below ground to ensure they are corrosion resistant if the soil conditions are aggressive. Furthermore, care should be taken both to avoid connecting two elements made of different metals to minimise risks of corrosion, and also to limit damage to the coating by careful handling.
Rock fall protection netting was successfully used, together with other systems, in the redevelopment of a former chalk quarry near Dartford in Kent. It had to be accepted that the near vertical quarry faces will suffer some localised erosion, but they needed to be made safe. The faces were draped with a wire mesh system to encapsulate falling debris.
The construction of two settlement ponds at two locations on the M4 required steepening of existing embankments to 60 degrees. Soil nailing was used in conjunction with a facing galvanised steel mesh and an erosion control matting.
- BS EN 14475:2006 Execution of special geotechnical works – reinforced fill
- BS 6031:2009 Code of practice for earthworks
- BS8006-1:2010 Code of practice for reinforced soils and other fills
- DMRB Volume 2 Section 1 Part 5 (BD 70/03) Highway structures: Design (substructures and special structures), materials. Substructures. Strengthened/reinforced soils and other fills for retaining walls and bridge abutments. Use of BS 8006:1995, incorporating amendment No1
- DMRB Volume 4 Section 1 Part 4 (HA 68/94) Design methods for the reinforcement of highway slopes by reinforced soil and soil nailing techniques
- CIRIA Publication C591 Infrastructure cutting – condition appraisal and remedial treatment, London 2003
- CIRIA Publication C637 Soil nailing – best practice guidance, London 2005
- TRL Report 537 Soil nailing for slopes, Crowthorne 2002
- CIRIA Publication C637 Soil nailing – best practice guidance, London 2005
- TRL Report 565 The response of a reinforced soil wall to differential movement, Crowthorne 2003
