Nailed wall

A soil nailed retaining structure stabilizes and reinforces the soil mass in situ. The technique consists of inserting and grouting - usually subhorizontally - closely spaced slender steel reinforcing bars or “nails” typically anchored in a steel grid reinforced shotcrete facing applied on the excavation front in order to provide continuity in support. Soil nail walls are relatively flexible, suitable only for excavation above groundwater.

Construction sequence

Excavation one level after another

1. Initial excavation of a small, unsupported cut, typically 1 to 2 m high and installation of the reinforcement mesh

2. In situ soil reinforcement by installing and grouting of not pre-tensioned, passive elements or ‘nails’, immediately followed by placing the facing element, i.e. shotcrete

3. Construction of the subsequent excavation levels, installation of the next rows of nails and projection of concrete facing until the wall has stabilized

4. Final nailed wall

Fields of application

• Soil reinforcement, construction of earth retention support systems

• Suitable for confined areas with difficult and restricted access

• Underpinning and stabilization

• Realization of high and/or steep cuttings to maximise development space

• Not usable in soils without short-term cohesion because soil nail walls require soil (slope, excavation) deformation to efficiently mobilize the soil nail forces

Environmental impact

• Vibration-free

• Soil removal

• Limited to working areas without presence of groundwater table during the excavation

• Protection of the immediate surroundings when projecting shotcrete (buildings, compounds, …)

• A stable, dry and flat work platform is needed

Technical specifications

• The surfaces between the nails are stabilized by applying reinforced shotcrete

• Nails and shotcrete are progressively installed as the exaction works progress

• The result is a gravity wall, almost vertical or inclined

Related projects

ETTERBEEK, BELGIUM

Etterbeek City Hall

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