Dinorwig Power Station Dam Grouting | Piling Contractors | Keller UK

Dinorwig Power Station Dam Grouting

Built in 1970’s, Marchlyn Dam acts as a pumped storage reservoir for Dinorwig Power Station, in North Wales. To meet increased electricity demand, a decision was taken to increase the height of the dam, and as part of the upgrade, also to seal leaks that had developed on both abutments. This required the installation of a grout curtain to 110m depth. With the dam acting as a storage reservoir, the reservoir level fluctuated up to 30m per day which necessitated grout selection and phasing of grout injections to meet such high head fluctuations.

Installation of up to a 110m deep grout curtain cut-off was conducted to both abutments of the existing rockfill dam, using an Ascending Stage technique. The slate was highly fractured, so grout holes had to be carefully drilled to reduce problems of borehole collapse and achieve required positional tolerance.

Grout design also had to consider the wash-out effects on pollution of downstream watercourses, and avoid damage to dam wells and monitoring. Consequently, Microfine grout was used above 40m depth, and Mayco Silica below 40m. Critical grouting operations were phased to tie–in with reduced periods of electricity demand.

Grout design had to consider the hydraulic effects of fluctuating ground water levels from the pumped storage scheme. Water levels within the reservoir fluctuated by up to 30m over a 24 hour cycle during drawdown stage and refilling for electricity production.

Post-treatment testing of the grout curtain was conducted using cored holes, with double packer in-situ Lugeon testing. 

The operations were conducted in an environmentally sensitive area where protection of watercourses and reservoir were paramount. Site wide environmental controls were developed by Keller and the project was completed without incident.

Systems: Grouting / Dam Grouting

Client: First Hydro Company

Contractor: Keller Geotechnique

Engineer: Mott MacDonald

Year of Execution: 2012


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