Great Western railway electrification, UK: Patchway tunnels

The Patchway rail tunnels in Bristol were a major obstacle to the £3 billion electrification of the Great Western railway between London and south Wales, completed in December 2019. The tracks in the three nineteenth-century brick-arch tunnels needed to be lowered to provide the required clearances for new overhead line equipment. Extensive surveys, stability analyses and strengthening measures were undertaken to ensure structural integrity was maintained during the track lowering. An overhead conductor bar was developed specifically for the tunnels to reduce the lowering required. Further innovation included specially adapted drilling rigs to enable the efficient installation of tunnel fixings. This paper focuses on the civil engineering aspects of the project, with an overview of the electrification design to demonstrate how the overall integrated solution was achieved.