FP McCann on behalf of NI Railways have recently completed a second phase of works on a Pilot Scheme carrying out repairs to the Castlerock and Downhill Railway Tunnels

Title: Castlerock and Downhill Railway Tunnel Brick Arch Repairs

Principal Contractor: FP McCann Ltd.

Contracts Manager: Seamus O’Sullivan

Principal Designer: AMEY Consulting

Description: FP McCann on behalf of NI Railways have recently completed a second phase of works on a Pilot Scheme carrying out repairs to the approximately 175 year old masonry arch or barrel vaults of both the Castlerock and Downhill Railway Tunnels caused by decay of the original mortars and water ingress.

A brief history of the Castlerock and Downhill Tunnels: The Famous railway engineer Robert Stephenson (son of George Stephenson) and architect Charles Lanyon were commissioned to undertake initial surveys for construction of the two tunnels at Downhill and Castlerock.

Construction of the Castlerock and Downhill Railway Tunnels commenced in 1846 using traditional tunnelling and mining techniques to excavate the tunnels, alongside the use of explosives to remove large quantities of rock.

The first blasting at Downhill is recorded to have occurred in November 1845. In July 1847 the western tunnel, i.e. Downhill Tunnel was completed, making it the first railway tunnel in Ireland ready for use.

A local brickyard in neighbouring Articlave employing 150 local men supplied the bricks used to line both the Castlerock and Downhill Tunnel arches or barrel vaults. On the 18th July 1853, the Derry/Londonderry to Coleraine railway was finally complete, eight years after the project had begun.

The Castlerock tunnel is approximately 668yds (611m) in length and is recorded as the longest operational railway tunnel in Ireland. After passing through a short opening trains then pass through the shorter Downhill tunnel which is 301yds (275 m) in length.

FP McCann Castlerock Downhill Completed Brickwork Repairs

For this repair pilot scheme, FP McCann were engaged by Translink to;

Appoint & manage Temporary Works Designers to design a proposal for ‘Brickwork Recasing Centering’ (Centering is the formwork used to support the masonry on an arch or barrel vault while the masonry is placed and before it has gained sufficient strength to support its own weight).
Undertake a Gauge assessment of both tunnels.
Fabricate/manufacture the approved ‘Centering’ to undertake ‘Single Ring Brickwork Recasing’ repairs to the masonry arch or barrel vault of both the Castlerock and Downhill Railway Tunnels.
Complete onsite ‘Pull Out Testing’ and provision of reports on the proposed temporary works fixings to be used in conjunction with the proposed ‘Centering’ to ensure a performance compliance with the temporary works design.

Complete deep cleaning of the tunnel masonry arch or barrel vaults removing soot build-up and other detritus to allow further examination and defect identification by the NI railway Structural consultants.
Complete repairs to the tunnel masonry arch or barrel vaults including ‘stitching and grouting of fractures, cross pinning stitching and grouting, repointing of joints, and clay brick masonry replacements utilising reclaimed bricks.
Undertake ‘Pull out Tests’ of any Permanent Works Fixings used in the structural repairs.
Carry out drainage repairs and installation of newly designed roof drainage pans and associated discharge pipework.