A call for bids to perform two years of tunnel lining repair work over all 21km of Glasgow’s twin-tube underground metro is issued by the owner and operator, Strathclyde Partnership for Transport (SPT).
Deadline for competitive bids was originally 18 July but is extended to 4 August. It is expected that the bid assessment and contract award process will last until at least late October, and the works begin shortly after.
The package of works is for system-wide improvements on the total 21km tunnels (2 x 10.5km), and is to NEC3 contract conditions with a remeasurable element, said SPT senior project engineer Eric Thomson.
Tenders are to a sample design by SPT in conjunction with its consultant Donaldson Associates. Bids will be assessed on weighed economic value, confirmed Thomson.
Glasgow underground metro was opened in 1896, and is the world’s third oldest after London and Budapest. It has twin 3.35m i.d., mostly concrete- and brick-lined tunnels, following a circular route around the heart of the city, twice crossing the River Clyde. The metro has 15 stations. From beginnings as a cable-hauled system, it was only converted to electric power in the 1930s, and underwent a round of modernisation in the late 1970s.
The scope of the latest large-scale works, currently under tender in the lining refurbishment package, include repairs to the structure and track-bed, and also improvements to drainage, around the entire underground route.
Activities involved in the works include: probe hole investigations to detect possible voids behind the lining, establishing the thickness of the structural lining, removing drip sheets to investigate the condition of the lining, and inspection of the cleaned track-bed, slips and drainage channel for water ingress problems with silt/sand, considered a potential issue in the south of the metro system.
The principal remedial works envisaged include: final design to suit conditions established on site; patch concrete and shotcrete strengthening to the lining; infilling voids behind the lining with concrete grout; installing weep pipes to manage water ingress and pressure; and, chemical resin injection to seal the lining and further minimise water ingress.
SPT’s latest lining improvement contract follows the recent completion of a shorter works package between Buchanan St and Cowcaddens stations. The works were completed by Balvac, a Balfour Batty subsidiary. Balvac previously worked on the Kelvinhall to Partick section, and also on waterproofing tasks on other sections.
“There are more works in the Buchanan St to Cowcaddens section of similar type, and the system-wide works have an element of what we have done within the Buchanan St section,” said Thomson.
He added that the lining improvements contract is one of a few packages under tender at present on the metro, the others including pumping stations, trackworks and chainage.