The A465 Heads of the Valleys Road: DYWIDAG Systems permit efficient Reinforcement of steep Earthworks Cuttings

The A465 Heads of the Valleys Road is an important trunk road connecting Southwest Wales and the British Midlands. In order to promote growth in rural areas of Wales such as Ebbw Vale, investment has been provided by the Welsh Government to upgrade the route. The overall project has been split into several phases with Section 2 currently under construction. The project primarily consists of upgrading 8km of road to allow two lanes of traffic in each direction between Gilwern and Brynmawr.

The topography varies over the 8km site, and in some areas, large amounts of loose overburden overlie rock. DYWIDAG-Systems International UK supplied 240t of R32-360 DYWI® Drill Hollow Bars to stabilize the slopes in this area. The variable geology of the site has made installing the DYWI® Drill Soil Nails challenging for the three specialist geotechnical contractors, BAM Ritchies, CAN Geotechnical and Quantum.

Due to the topography and fragmented nature of the underlying rock head, the soil nail design was reviewed by the principal designer on a regular basis. In order to make the DYWI® Drill Soil Nail spacing as efficient as possible, after nailing, the reinforced cutting slopes were faced with DSI supplied hi-tensile Deltax Rock Netting.

In total, approximately 100,000m² Deltax Rock Netting was used in addition to 5,000m² of DYWI® Mat Erosion Control Matting.

Deltax offers resistance against shallow failure of the slope surface and provides a mechanism of transferring load from the slope to the soil nails. The ability to transfer load efficiently comes down in part to the low strain characteristics of the hi-tensile wire used to make the mesh. In some scenarios, the use of hi-tensile meshes such as Deltax can allow for the DYWI® Drill Soil Nails to be spaced further apart, making the solution more economical for the Client.

Owner

Welsh Government

General Contractor

Costain Ltd, Great Britain

Specialist Geotechnical Contractor

CAN Geotechnical Ltd, BAM Ritchies Ltd and Quantum – Geotech, all of them Great Britain

Consulting Engineers

Atkins/CH2M Design Joint Venture, RPS Group Plc, all of them Great Britain


Unit

DYWIDAG-Systems International Ltd., Great Britain

Scope

Production, supply, technical support

Products

240t of galvanized R32-360 DYWI® Drill Hollow Bars, 100,000m² Deltax Rock Netting, 5,000m² of DYWI® Mat Erosion Control

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