This contract was let at the same time as the Advanced Earthworks Contract for the Trent Approaches and involved the same contractor and supervisory teams.

Thorne to Sandtoft (J1 to J2)

The contract was awarded to A. Monk & Co. Ltd. in the sum of £4.8m on 3^rd May 1976. The contract period was 24 months.

The Works consist of the construction of approximately 7km of dual, 3 lane motorway together with the addition of a third lane for approximately 1km to the existing A18(M) trafficked motorway. The Motorway has dual carriageways 11m wide with a 4m central reserve. There are two outside margins of 4.8m comprising of a 3.3m hardshoulder and a 1.5m verge. An advanced earthworks contract was completed near to the County boundary, overlying the alluvial plain of the Old River Don. Surcharge was removed from this embankment at a late stage in the Contract.

There is one partial interchange at Tudworth affording facilities for Westbound traffic to join and Eastbound traffic to leave the motorway.

Two side roads, A18 Doncaster to Scunthorpe Trunk Road and Crow Tree Bank together with two accommodation tracks were diverted on embankment and bridges over the Motorway.

Tudworth Road Bridge over the M180, a 2 span structure carries the A18 at a 25° skew. The deck consists of prestressed M-beams with an in situ concrete deck slab supported on reinforced concrete abutments on spread foundations.

Crow Tree Bank bridge, a 4 span structure carries an unclassified road at a 5° skew. Reinforced concrete skeleton abutments and piers founded on driven piles support a similar deck to that above.

Dale Mount and Plains Lane Bridges are 3 span square accommodation bridges having similar support structures. The deck consists of 3 T-beams with reinforced concrete slabs. The side and cantilever spans are reinforced concrete with half joints supporting prestressed post-tensioned suspended spans.

Three 2.9 metre diameter Armco multiplate culverts were constructed to maintain the flow of the existing main drainage together with numerous smaller culverts.

The site of the Works generally overlies Bunter Sandstone covered by a mixture of alluvium, peat, wind blown sand, clay, silts, sands and gravels, some of which are glacial deposits. Extensive treatment was necessary in certain locations to minimise the effect of the underlying alluvium and peat particularly in the disused watercourses. Generally the land is flat and has been substantially improved by man made watercourses leaving many disused channels. Substantial drainage ditches were excavated on each side of the Motorway and major improvements involving the construction of new channels, flood banks and pump houses were provided by the Severn - Trent Water Authority to accommodate the drainage from the M180 and M18.

The Motorway is generally on shallow embankment approximately 2 metres high. There is one small cut section adjacent to the A18 where the motorway passes through Tudworth Hill. Excavated material from the cutting and the ditches was where possible, used in the embankments. Unsuitable material was deposited in landscape areas and on a noise bund at Tudworth. Tree planting was carried out on completion of this Contract. Additional filling material for the embankment was obtained from workings adjacent to the route. The amount of excavation in the Contract was 400,000 cu. m and the filling required was 760,000 cu. m.

The construction of the Motorway pavement was fully flexible and consists of 100mm of Rolled Asphalt surfacing. 230mm of bitumen macadam base on varying depths of sub-base.

The contract was completed on the 30^th May 1978.

The contract was awarded to Sir Alfred McAlpine & Son (Northern) Ltd in the sum of £6,783,300 and work started on the 1^st November 1976.

The contract involved the construction of dual three lane motorway between Sandtoft and the River Trent together with a grade-separated 'diamond' interchange at Woodhouse. The carriageways of the motorway are of rigid construction, the majority being experimental Continuously Reinforced Concrete Pavement, (CRCP), of varying depths and reinforcement position, with the remainder as comparative lengths of unreinforced and reinforced pavement with variations to joints and underlay. The hard shoulder is also unreinforced concrete pavement. The experiment was monitored by the Transport and Road Research Laboratory. Only 340 lin. m of the motorway are flexible, at either side of the two underbridges and at the tie-in to the adjacent Thorne-Sandtoft section. The slip roads and side road diversions are of flexible construction. The overall width is generally 35.6m, consisting of dual three lane carriageways, central reserve, hard shoulders and verges including where necessary a drainage channel. The slip roads at the Interchange have an overall width of 12m, including carriageway, hard strips and verges. The three main side road diversions are North Idle Lane, (unclassified), the A161 and Mutton Lane (C108). Two private accommodation bridges were constructed over the motorway to provide for adjacent farmers.

This length of motorway crosses over flat agricultural land which is generally only 1 to 2 metres above O.D. and consists of wind-blown sand at the western end and alluvial clays peats at the eastern end with the underlying Keuper Marl of the Permo-Triassic Series surfacing in the central area which forms part of the old Isle of Axholme. The marl is divided into two by a deposit of alluvial sands.

The motorway is basically formed on shallow embankment throughout, apart from the central Interchange area where superior ground conditions permit construction at or near ground level or in very shallow cutting.

On completion a total of 900,000 cu. m of fill, generally marl from existing sources at local brickworks, was imported.

In the past, in order to drain the land, a close and complex network of artificial channels and pumping stations had been constructed. The slow moving water in these channels is below the level of the water in the floodbank-enclosed river except at low tide, and pumping stations were used to discharge into the River Trent . Because of the increase run off resulting from the paved motorway it was necessary for the local Internal Drainage Boards and River Authority to improve the whole drainage of the area.

Carriageway and embankment drainage is carried by side ditches dug along both sides of the motorway and intersected by culverts.

Continuously Reinforced Concrete Pavement had not been used on a major road contract in the United Kingdom, except for two short lengths on the M62, Balkholme to Caves contract previously described. Seven lengths were involved, each approximately 1.6km long and set in a new UK record for CRCP.

The principal to promote hairline cracking at frequent intervals of 1.5 to 2.0m with a relatively heavy longitudinal reinforcement (0.6% by area) restricting the cracks to a width which maintains aggregate interlock load transfer and not require sealing has been discussed. The resulting increased flexibility of the slab will cope with any settlement of sub-soil which may incur. The basic design was developed by the Transport and Road Research Laboratory and was refined by the West Yorkshire Sub-Unit at the design stage of the contract.

The overall carriageway construction depth is 460 mm, the CRCP being 210mm, 230mm and 250mm thick, the remainder made up in sub-base, for which the Contractor used the Cement Bound Granular alternative. There are two lengths of identical thickness, one containing the reinforcement at mid-depth and the other at 1/3 depth. There is an additional section containing fabric reinforcement 7.6km long. The unreinforced concrete hard shoulder was paved after the 11.2 metre wide slab by a mini-paver, which also constructed the trapezoidal drainage channel at the same time. Elsewhere, the overall rigid construction depth is still 460 mm, but is made up of 180 mm unreinforced or reinforced pavement and 180 mm unreinforced or reinforced pavement and 180 mm sub-base. A length of the unreinforced pavement has narrow, unsealed contraction joints 3 mm wide and no polythene underlay.

Two types of terminal treatment for the CRCP slabs formed part of the experiment, with terminal anchor blocks provided to restrain movement, and wide flanged beam joints to allow the slab to move freely.

Concrete mix designs for the pavement involve the supply of some 96,000 tonnes of course aggregate, 60,000 tonnes of fine aggregate and 25,000 tonnes of cement. Stockpiling of materials on site began in January, 1978 with paving commencing in April 1978.

Concrete mixed on site used a Rex automatic batching plant incorporating a 7.5 cu. m capacity tilting drum mixture. Mixed material was transported to the paver using purpose made four axle non-tipping ejector trucks with 7.5 cu. m capacity to match the batch size. The trucks fitted with hydraulic actuated sliding ejector bulkheads and tailgates enabled rapid but controlled discharge into the paver.

The principle element in the paving unit was a wire guided Gunter and Zimmerman slip form paver incorporating a 2 metre long conforming plate, capable of laying the 11.2 metre wide slab. The machine ran on a pair of crawler tracks and was adjusted for line and level by wires which were positioned outside the machine. The unit was also capable of forming the longitudinal joints. Other units used, as and when necessary, were a transverse joint finisher and a combined brush texturing and curing spray machine, all of which were carried on rubber tyres and were wire guided.

The hard shoulder has a colour contrast red slurry and seal finish.

All bridges to the west of the Woodhouse Interchange are founded on piles driven to the underlying marl and associated gravels with the remainder on spread footings. It was originally envisaged that steel H-piles would be the most economic solution. However the Contractor proposed the use of Balken pre-cast segmental concrete piles type 7A and these were successfully substituted.

Of the seven bridges on the contract five have decks of prestressed concrete M-beams with an in situ reinforced concrete deck slabs. Reinforced concrete abutments were used for all bridges two being of skeleton type. Piers were of the reinforced concrete wall type.

North Idle Lane and Mutton Lane Bridges are similar and have four spans and carry unclassified roads.

Hatfield West Drain Bridge carries the motorway and has a span of 11m. Woodcarr Farm and Belwood Farm Bridges carry farm accommodation roads. The side and cantilever span beams are reinforced concrete with half-joints supporting pre-stressed post-tensioned suspended span beams.

River Torne / South Engine Drain Bridges of 2 spans carries the motorway over the river and the drain.

Woodhouse of 2 spans carries the A161 road over the motorway and has forward sloping faces and a central pier founded on spread footings. A 6.3m span Armco pipe arch with concrete headwalls carries the motorway over Folly Drain and a 2.1m diameter Armco pipe provides pedestrian access.

The contract was completed on the 9^th October 1978.