Introduction

A scheme for a northern by-pass of Tamworth, discussed for many years, was finally incorporated in 1968 into a larger scheme for a link between M5 and M1 Motorways which the Department of Transport was then considering. This link road was given motorway status and designated M42 in September 1970.

The 9.5 kilometre length of M42 from the A446 at Curdworth to the A5 South East of Tamworth has become known as the Kingsbury Section. Between 1971 and 1974 statutory procedures were followed for the provision of a dual three lane motorway for the M42 but subsequently changes in the design capacity of highways and revision of national forecasts of traffic growth led to a change to a dual two lane scheme. Revised plans were published in 1978 and these were subjected to Public Inquiry in 1980.

All this work on the Kingsbury Section was carried out by the Staffordshire Sub Unit of the Midland Road Construction Unit. In 1982, with the disbandment of the Road Construction Units, Sir Owen Williams and Partners were appointed to take over the detailed design and supervision of construction of this section. They completed the detailed design and preparation of contract documents by mid 1983 when it was put out to selected tender. Alfred McAlpine Construction Limited (South Region) were awarded the contract Tender Value: (valued at £16.75m) for completion by June 1986.

The scheme was opened, on the 18th December 1985 by the Right Hon Linda Chalker MP, the then Minister for Transport.

Terrain and Notable Features

The terrain is pleasant relatively featureless agricultural land mainly on gravels and sandstone. Immediately north of Curdworth roundabout the road is in a large cutting through sandy gravel materials with a high water table. For the next two kilometres it is generally at or near existing ground level until it reaches Bodymoor Heath Lane. This lane has been lifted over the motorway which then runs through Kingsbury Water Park to the River Tame. The Water Park is an environmentally sensitive area providing a recreation area important to the district It has been created by the natural regeneration of worked out gravel pits and has been conserved to provide a pleasant area for fishing and nature conservancy. Through these ponds extensive work was required to drain the line of the road and to remove unstable silty material from the old pits. To reduce the effect of the motorway on the Water Park users extensive sloped mounding was constructed on both sides of the route with pedestrian access being maintained by a subway.

After crossing the River Tame, which was diverted onto a new line, the road passes under the A51Tamworth Road before climbing to pass over the Birmingham to Derby Railway. To the north of the railway the route runs mainly in cutting in sandstone through agricultural land. The northern termination of the section includes a large grade separated roundabout junction on the A5 to the east of Wilnecote.

Concrete Carriageways

The carriageways of the Kingsbury Section are constructed of 280mm of unreinforced concrete except over structures where they are of bituminous construction. Side road diversions also have bituminous surfacing. Bituminous or concrete construction alternatives were billed for tender and the tendered prices favoured concrete.

The 199,000 square metres (approximately 130,000 tonnes) of concrete were laid over the full 17.6 kilometre length of 113 metre wide carriageway in under two months from 17th June 1985 to 7th August 1985. It was laid to full depth at a single pass using a Guntert und Zimmerman slip form paver comprising four units.

Concrete was batched on site in a seven cubic metre tilting drum mixer, and delivered by up to sixteen seven cubic metre end ejector trucks. The trucks discharged onto a short conveyor which fed a second, pivoted, conveyor. This was specially designed to allow distribution of the concrete continuously across the width of the paver. The paver ran directly on the sub base and had travelling side forms for concrete edge support. Finished concrete levels were controlled through a servo mechanism operating from tensioned wires.

Structures

There are fifteen bridges and eight pipe culverts in the Kingsbury Section. All of the bridges, except the small span subway at the Kingsbury Water Park utilise precast prestressed concrete beams in their decks. The Water Park subway is of reinforced concrete box construction.

The longest bridge carries the motorway over the River Tame and its flood plain; it has three spans each of twenty-seven metres. The deck is in standard section precast 'U' beams cast composite with an in situ reinforced concrete deck slab. In addition to the bridge are two flood relief crossings, one of two spans and one of single-span utilising precast T beam deck construction.

The mainline Birmingham to Nottingham railway is crossed by a single span bridge decked with infilled precast inverted 'T' beams whose flanges form a permanent soffit support for the in situ concrete.

Overbridges generally utilise precast T beams beneath the over road carriageway and special U beams at the edges of the decks supporting the footways and parapets. The beams are composite with an in situ reinforced concrete slab poured on permanent glass reinforced ribbed plastic sheeting spanning laterally between the beams.

Piers and abutments of all the bridges are reinforced concrete poured in situ. All wing wall faces have a vertical grooved finish which conceals construction joints and tie hole marks.

Foundations for four of the bridges are supported on the reinforced concrete cast in place bored piles. The remainder of the bridges are on spread foundations in sandstone or gravel strata.

In order to confirm pre-contract site investigations carried out by the Midland Road Construction Unit further site investigation work to a depth of twenty five metres below Structures bridge foundation level was carried out with the main contract, As a result old mine workings in the area adjacent to Birmingham to Derby Railway were treated by grouting.