VALLEY FARM BRIDGE

2008

 

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Valley Farm Bridge                                        Grid Ref SE 324 297

A61 over A639, Leeds                                   Date of Construction 1970 / 71

A61 LEEDS-WAKEFIELD Road OVER A639 PONTEFRACT-LEEDS ROAD

This bridge is a special one for me. I designed the substructure i.e. abutments and foundations and submitted the design as part of my submission for Chartered Civil Engineer to the Institution of Civil Engineers. As part of my site experience for my I.C.E. interview I included in my  report  the construction of the Stourton Link Road.  The scheme comprised the construction of a 1 mile of new dual carriageway from John o’ Gaunts on the existing A639 at Rothwell to  the Stourton Interchange bridges on the M1 motorway (now renumbered M621) at an overall cost of  £1.25 million. Valley Farm bridge, Rose Cottage Farm bridge (now infilled) and rose Cottage Farm underpass were also included in the scheme. The deck of Valley Farm bridge was designed by my colleague Peter Sugden, both of us reporting to David Garner M.I.C.E.


Valley Farm Bridge is unusual for its skew of 45 deg., dictated by the layout of the roads in the interchange with the M1 motorway. It is also unusual because, as bridge engineers, we insisted that its location be changed in the early stages of the scheme design to avoid the north abutment being sited in opencast backfill. The south wall of the Stourton opencast coal mine is located immediately to the north east of the bridge in its current position.


The bridge  abutments are reinforced concrete cantilevers on spread footings founded on sandstone. The  heavily skewed footprint of the abutments produced high bearing pressures in the obtuse corners in plan,  due to earth pressures behind the abutment wall. I analysed this effect using a set of skew axes in plan, much to the surprise and admiration of my supervising engineers. The long cantilevering wing walls offset the overturning effect from the earth pressures on the rear face of the abutment walls.


The deck consists of pre-tensioned (deflected tendons) prestressed concrete beams with a composite reinforced concrete slab. The beams were precast in Fairclough’s factory in Accrington, using the same moulds as standard M62 bridge beams. The M62 motorway in the West Riding was under construction at this time.


Deck waterproofing proved troublesome. The contractor used the  specified Mastic Asphalt, but he was unable to control the appearance of large blisters appearing as the asphalt cooled. The cause was believed to be residual water vapour in the new concrete. The blisters were treated by puncturing and relaying a patch. The deck movement joints were specified as epoxy nosings with a filler, perhaps ‘Compriband’. The nosings broke up and were  replaced in the 1990s, I think.


Another important part of the Stourton Link Road was the construction of the  westbound cut at SE339294 on the B6481 Pontefract Road. The cut was of the order of 10m deep into saturated sandy gravel. The material was excavated by front and rear engined motor-scrapers bought by Budge specifically for the contract. The water content was so high that the material only became suitable for fill in embankments after it had been spread in thin layers and allowed to dry out in the sumer sun.  Extra large diameter drains were required at the bottom of the cutting to carry the constant flow of water which continued after the contract was completed.


Unfortunately, all this construction has now been buried when the junction with the B6481 was remodelled for the current M1 junction 44.


The contractor for the works was  AF Budge of Retford.


I acted as Assistant Resident Engineer, supervising the work on behalf of the County Surveyor of the West Riding of Yorkshire County Council. The Resident Engineer was John Firth M.I.C.E. and our Q.S. was Ron Whittaker. During the contract Ron lived in a caravan in an old quarry on the south side of the site, where the M1 motorway now runs. The quarry was an oasis of peace and tranquility. Ron had previously been the Q.S. on the A1 Ferrybridge By-pass when the contractor went into liquidation; he taught me all I needed about quantity surveying to pass my Chartered Engineer interview.

Location Map        Valley Farm Bridge


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