Page 27 - Hub-4 Magazine Issue 80

Concrete Review
Mullardoch Tunnel Restoration
Cemex recently provided a special, high- performance blend of Dry Sprayed Concrete with reinforced steel fibres, to assist in the complex and successful restoration of the Mullardoch Tunnel project, in the Scottish Highlands.
The Mullardoch Tunnel, running from Tomich to Cannich, is located approximately 25 miles south- west of Inverness. It provides access to the hydro- electric scheme at Fasnakyle Power Station which was initially built in the 1950’s as part of the North of Scotland Hydro-Electric Board's drive to provide electricity for northern Scotland. The tunnel was constructed by drill and blast methods through the rock which at the time of construction was a highly ambitious build, providing stable access routes through the remote and mountainous valley.
As part of the ongoing tunnel management and maintenance inspections, a defective area of rock was identified in 2019 which needed large-scale repair. A collapse inside the tunnel would pose major operational issues for the nearby power station, with far reaching effects. A programme of repair was required to stabilise the tunnel using rock bolts and finished off with a bespoke high performance blend of reinforced dry sprayed concrete.
The advanced Cemex lining product was proposed by sprayed concrete specialist Gunform International Limited and formulated in close partnership with Cemex. The material was supplied in 1000kg bags and installed using a big bag dispenser and Reed LOVA Gunite Machine. The Cemex material, with an internal accelerator, was applied in thickness up to 500mm thick to create a regular hard-wearing finish. The main contractor for the Mullardoch Tunnel project was AMCO-Giffen Ltd and the client was SSE plc (formerly Scottish and Southern Energy plc).
Access to the tunnel site at Mullardoch was extremely restricted which posed additional
challenges. It was imperative for Cemex to meet the demands on site and the project completed on time. Cemex’s high performance fibre reinforced concrete offers bespoke design solutions incorporating a 3- Dimensional system of either macro-synthetic or steel fibre reinforcement, which reduces the risk of cracking, increases impact and shatter resistance, improves surface durability and reduces long-term maintenance costs. At Mullardoch, the Dry Spray Concrete product arrived on site each time with the fibres evenly distributed throughout the product, allowing the time-saving process of placing concrete and reinforcement in a single operation.
Cemex’s tailor made fibre reinforced concrete is produced to suit specific customer needs and manufactured in accordance with BS EN ISO 9001, BES 6001 and BS EN 14889. It is independently certified under the Quality Scheme for Ready Mixed Concrete (QSRMC) in accordance with the relevant standards and is available from Cemex plants throughout the UK.
Specialist Technical Support
In addition to sprayed concrete primary lining solutions, Cemex has extensive experience in designing, producing, and delivering concrete across all tunnelling related structures. The company has proficient experience and capability in providing sprayed lining solutions and can produce both cast in-situ or sprayed concrete products delivered in a pre-blended dry silo.
All specialist technical support and laboratory testing is performed by a Cemex team of UKAS accredited technical experts providing comprehensive solutions for all testing requirements, from approval to continuous compliance and investigations. Our centrally located facility enables nationwide site testing, and is backed by wider specialist resources and technical expertise from our global Cemex business.
For more information www.cemex.co.uk
www.hub-4.com May/June - Issue 80
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