MERSEY TUNNELS REFURBISHMENT AND UPGRADING

Queensway, the first road tunnel under the Mersey Estuary in England, was opened in 1934, and the second, Kingsway, in 1971. This article describes some of the more significant work in refurbishing and upgrading these aging tunnels. Queensway is about 4km long, and its 13.3m diameter main tube carries four 2.7m wide traffic lanes. Under the river, the tube is made of bolted cast iron segments, but, under the land, it also uses some precast concrete segments. The ventilation airways and shafts, and the pumproom caverns are mostly cast iron, with some steel-reinforced concrete. All the main structures are in good condition, but there is some structural deterioration, mainly in the concrete. Kingsway is 2.2km long, with two 9.6m diameter tubes each carrying two 3.6m wide traffic lanes. Most of the structural envelope of road tube and airway is precast concrete bolted segments, caulked with cemented asbestos. The concrete is suffering chloride attack, and there are potentially serious problems with the caulked and road-deck joints. The article details the refurbishment, renewal, and major repairs of the tunnels. It also discusses Kingsway's monitoring, control, and communications technology. All the work was done under very difficult working conditions, and applied the principle "Keep it simple and robust".