Weaver Viaduct

Weaver Viaduct is one of the outstanding features of M56 and its design was approved by the Royal Fine Arts Commission. The three-quarter mile of elevated motorway and approach embankments over the River Weaver and Weaver Navigation Canal opened on 21 February 1971 along with the 5 mile section from J12 Sutton to J14 Hapsford.

Viaduct construction

The viaduct is 971 metres (3,186 feet) long and has 33 spans. The canal crossing has a central span of 67.7m (222 ft) and two side spans of 38.1m (125ft). The river span is 38.1m (125ft). It has 18.3m (70 ft) navigational clearance over the canal and 6.7m (22ft) over the river. The normal width of the deck was 34.1m (112 ft) but it was wider at the north-east end to accomodate the slip roads at J12.

The approach spans were generally 27m (90ft) incorporating standard pre-cast, pre-stressed, concrete beams composite with a reinforced concrete deck slab. The main spans were cast in-situ pre-stressed concrete.

Because of the low bearing capacity of the ground, the piers were carried on concrete driven in-situ piles up to a maximum depth of 18m (60 ft), the depth at which rock was struck.

The pre-cast beams travelled to the site from the factory in Manchester. A purpose built gantry crane was produced by the contractors' structural engineers. Erected on the top of two adjacent piers the gantry crane ran out on rails to lift the gigantic beams into position. The gantry crane was then shifted to the next span. The gantry crane was not able to deal with the 100 ton river and canal span pre-cast beams and these were lifted into place using conventional cranes.

The 100 tons of scaffolding for the canal span was able to be skidded sideways along the canal bank to build the bridge span in sections, side by side. It enabled one-third of the span to be built at a time.

The viaduct had hard shoulders, unlike the Thelwall Viaduct on opening.

Contract details

Design was by Husband and Co., acting for Department of Environment, who also supervised the project.

The contractor was Christiani Shand (a consortium of Christiani and Nielsen Ltd, and Lehane, MacKenzie and Shand Ltd.) with a tender price of £3,146,387 in March 1968. The eventual cost was put at £3.5 million. Work began in April 1968.

Safety barriers

The Ministry of Transport had issued a statement about the advantages of central reservation safety barriers on bridges and so these were to be fitted from new. As of October 1970 it had not been decided if the rest of the motorway section should have them fitted. Barriers were fitted to the viaduct edges as with all motorway viaducts.