Wall Reinforcement - Weldgrip Epoxy Soil Nails

Project Title A5 Nant Ffrancon Wall Reinforcement Client Welsh Office Main Contractor Colin Jones [Rock Engineering Ltd] Featured Products Weldgrip Epoxy Soil Nails

The Nant Ffrancon wall stabilisation project is part of maintenance work to the main A5 trunk road in North Wales. The object of this Welsh Office project was to reinforce an existing stone wall running along the west side of the carriageway.

The project was specified in six phases, with work being carried out over a period of three years. The height of the wall increased with each phase, from 1.5m to 10m.

Part of the reinforcement for Phases 5 and 6 consisted of installing Weldgrip Epoxy Soil Nails into the wall and under the road. The nails are of a tubular construction, with an O.D. of 32mm and I.D. of 15mm. They have a tensile strength of 470kN and a shear strength of 190kN. The nails were installed into 76mm diameter holes and pumped with O.P.C. Cementitious grout.

Pump pressures of up to 55 bar were recorded.

To improve the aesthetics of the finished work, the nail end assemblies were countersunk into the wall, by overcoreing the holes, 250mm long by 150mm diameter. The end assembly consisted of a 125mm plastic plate and a nut capable of withstanding 90kN of end load. Nail lengths of 10m and 12m were used.

To validate the grout/rock interface a series of sacrificial pullout test nails were axially loaded to 140kN. Also 10 percent of the production nails were pull tested to the designed working load of 40kN.

The system advantages of using Epoxy tube were:

• Ease of installation
• The light construction enabled longer lengths of tube to be used
• High corrosion resistance
• Cost effectiveness

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Product Brochure - Soil Nails & Rockbolts - 620k

Weldgrip are also proud to have attained BBA accreditation and ISO 9001 standards in recognition of our continuing excellence in Geotechnical products and services.