Soil Nailing


Coffey Construction Ltd have the qualifications and experience in the concept of soil nailing, which briefly is to reinforce and strengthen existing ground by installing closely spaced grouted steel bars, called "nails," into a slope or excavation as construction proceeds from the "top down."

Technical Information:

This process creates a reinforced section that is itself stable and able to retain the ground behind it. Soil nailing works in tension, bending and shear.  Generally, the soil nails significantly increase the apparent cohesion of the soil through their ability to carry tensile loads. A construction facing is also usually required, and is typically shotcrete reinforced by welded wire mesh. This technique is also be used in rock, to anchor structures against the floatation reaction due to ground water.

Permanent Bar Anchor with Double Corrosion Protection
(Lifespan: up to 120 years)

Plant Description:

We have used a variety of different equipment to carry out the process. We have used the Wimmer Rock drill with the most effective results due to the versatility of the Unit. The Wimmer Rock drill is machine mounted on a 30 ton excavator and can Drill and install at any angle, through any material, from any position.

Coffeys Experience:

Soil Nailing Coothill, Cavan - Coffeys carried out Soil Nailing as part of a retaining Structure on a factory development in Coothill in Co Cavan

Drogheda Main Drainage - Coffeys carried out Soil Nailing as part of a retaining Structure on the Drogheda Main Drainage package in Drogheda in Co Louth

Athenry Mixed Use Development - Coffeys carried out Soil Nailing as part of a the installation of rock anchors as part of a sewer line for a Mixed Unit Development at Athenry, Co. Galway

Retaining Wall Stabilisation at Sorrento Mews, Dalkey - Dublin to Wexford Line -
Coffey Construction Ltd was the successful contractor appointed to carry out the works at Sorrento Mews, Dalkey by Iarnrod Eireann in November 2009.

Project Description -An existing masonry retaining wall showed sign of creep shown below. In order for to sustain the structural integrity of the retaining wall, stabilisation works were deemed necessary.

Emergency Works -Following heavy rain during the run up the Christmas the retaining wall began to slip by a distance of 75mm. A decision was made to remove the wall under emergency works before the inevitable collapse would have caused a major H & S risk to the public.

Scope -The works consisted of 61No. 40mm Diameter Hollow Soil Nail bars was embedded 6-8m into the ground of which the soil characteristics were made up of 5m of gravelly clay material and the remaining 2m was granite rock. The upper row of Soil Nails was installed at 300 and the lower row of Soil Nails installed at 400.

Innovation - Alternative Design -Coffey Construction Ltd proposed an alternative design by the use of Pre-cast panels in lieu of pouring concrete in-situ which would ultimately reduce the overall timescale for the project. The panels proposed were a product (See Figure .1.1) from Oran-Precast. These consisted of 2No. 65mm panels spaced apart by reinforcement all which was cast in factory conditions. The void in-between was poured Insitu once the panels were lifted into position. This method allowed longer precast panels to be designed as the weight of the member was significantly less than that of a solid precast wall unit.

Installation of Soil Nails - We carried out all the specialist works namely; Drilling, Grouting and Testing. The use of one of Coffey Construction’s many specialist plant items the excavator mounted drill (‘Wimmer Drill’) was used to carry out the works. the versatility of this drill was the key success to this project as works could be carried out in a safe and timely manner.

Testing -The lower line of soil nails was tested to a tensile load of 320kN and the upper row was tested to a load of 230kN. As per the specification and BS8081, 1/5 of the total no. of soil nails was tested where all results were successful. We carried out the testing with our own equipment.

Stone Cladding - In lieu of the ‘Reckli’ concrete finish that was originally specified, we proposed the use of an Architectural stone cladding facade. This was subsequently approved and specialist mortar was utilised due to the surface finish of the precast unit to achieve a sufficient bond.  

Coffey Group, Athenry, Co. Galway, Ireland Tel: +353 91 844356 Fax: +353 91 844519 Email: