Soil Nailing
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Contact information
- Anthony Lucas
- geotechnique@keller.co.uk
Soil Nailing provides a cost effective and efficient solution to many slope stability and earth retention problems. Employed extensively on highway/motorway widening schemes, the system is also frequently used by developers to create more usable sloping sites. Adaptable to difficult access sites and quick to install, Soil Nailing is a technique that works by reinforcing and strengthening existing ground. Each Soil Nail consists of a reinforcing bar that is generally made of steel (with full corrosion protection for permanent works) or alternatively can compromise reinforcement in the form of GRP or carbon fibre bars.
Keller also installs self-drilling hollow bar Soil Nails where conditions allow. Installed from the top down, the slope or required excavation is supported by the Soil Nails being put into tension as the ground deforms literally around them. Facing systems are generally required to protect the face of the cutting. These can compromise sprayed concrete or geo-mesh fabrics as required.
Keller offers a full hydroseeding service to provide a vegetated face along with a range of structural reinforced soil facings such as Timbacrib and Geolock Walls. Unlike Ground anchorages, Soil Nails are generally passive inclusions and are not post-tensioned; however testing to prove the bond capacity at the soil/grout interface is an essential part of the Soil Nail design process.
Testing works are carried out prior to or during the nailing works using sacrificial nails and should consist of the testing of the active and [passive zone of the soil nailed block. This data is then used to confirm and/or finalise the assumptions made in the proposed design. The testing of production nails is not recommended as this can affect their working properties.
What are the benefits?
- Using top down construction methods with each subsequent row of nails providing both temporary and long term support, the need for costly temporary works is avoided.
- Elimination of the need for expensive stone backfill imported to site.
- Existing structures and embankments can be stabilised without re-building, saving costs and maintaining serviceability, for example existing railways embankments.
- Trees, vegetation or architectural features can often remain unaffected by soil nails, as this can be sited to pass around or between obstacles.
Typical applications for Soil Nailing
- Stabilising steep cuttings to maximise development space.
- The stabilising of existing over-steep embankments.
- Soil Nailing structures through existing concrete or masonry structures as failing retaining walls and bridge abutments to provide long term stability with demolition and re-build costs.
- Temporary support can be provided to excavations without the need to bulky and intrusive scaffold type temporary works solutions.
