Marykirk Viaduct Masonry Repairs

The Project

Originally constructed in 1849, Marykirk Viaduct is a 13 span railway bridge in Aberdeenshire, carrying the Aberdeen–Dundee main line over the River North Esk. The substructure is constructed from stone masonry and is set on a skew of approximately 40 degrees.

Bell Access & Engineering were appointed by Story Contracting to carry out rope access masonry repairs and structural strengthening works to the viaduct as part of Network Rail’s CP7 Structures Programme. The works included masonry repairs to the wingwalls, parapets and abutments, together with the installation of spandrel tie bars through the wingwalls to improve the long-term stability of the structure.

Our Method

One of the main challenges of this job was drilling six 14 metre long core holes through voided masonry on a 40 degree skew. The drill rigs had to be set up accurately to ensure the core holes remained within the specified tolerance of +/-75 mm over the full length of hole drilled.

Another significant challenge was the installation of three 300 kg masonry blocks at the high mileage abutment. A Lewis lifting pin was used in conjunction with rope access techniques to safely lift and position the replacement masonry blocks within a confined work area, eliminating the need for larger lifting plant.

Works Undertaken

• De-vegetation of the wingwalls, parapets, abutments and the 5m envelope around the structure
• Stone indentation and lime mortar patch repairs to wingwalls, parapets, abutments and string course
• Raking out and repointing defective mortar joints using lime mortar
• Localised stone indent repairs including the replacement of three 300 kg masonry blocks to the high mileage abutment
• Total weight of masonry blocks installed: approximately 3 tonnes
• Diamond core drilling of 14 m long, 86 mm diameter holes through masonry with a skew of approximately 40°
• Installation of six DCP spandrel ties through the wingwalls

The Outcome

Industrial rope access was used as the primary access method, removing the need for scaffolding and minimising disruption to the operational railway. Detailed lift plans were developed for the installation of the 300 kg replacement masonry blocks, with a Lewis lifting pin and a Skylotec ICX battery powered ascender used to position the stones while minimising manual handling.