Station Road Underbridge MAC3/225

Work undertaken

Brief Description

MAC3/225 Station Road Bridge carries a single track Cleethorpes to Nunnery Main railway line over Station Road at 79m 0099yds running between the villages of Blyton (to the North side) and Pilham (to the South side) which are located to the North East of Gainsborough in Lincolnshire.

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Overview of the work completed

The original construction was two singlespan bridges constructed of steel with twin longitudinal main girders, cross girders and rail bearers on brick abutments. Constructed around 1906, one bridge carried live load and one was redundant with the tracks removed. The bridge was in poor condition with evidence of water ingress at the deck ends which had resulted in extensive corrosion. The main girders and rail bearers had significant areas of loss of section to the stiffeners, bottom flanges and, in particular, the webs, which in some locations were beginning to extend into the bearing zone. The Client, Network Rail, were concerned about the on-going deterioration of the existing bridge, and it was determined that the most economical course of action was to replace it.

The bridge reconstruction was to be integrated into the North Lincolnshire Re-signalling Blockade. The fact that the works had to be carried out over Christmas meant that a significant amount of planning and risk evaluation was required.  By utilising this opportunity, CML was able to optimise the planned access, removing the need for future disruptive possessions and therefore reducing the impact on train operators and customers alike.

Work to replace the bridge began in earnest when the worksite was granted at 22:00 on Christmas Eve. The first works involved disconnection of the track circuits followed by the removal of the track, ballast and other materials from both bridge decks. The old bridges were picked up as one and transported to the site compound by a Self Propelled Modular Transporter (SPMT). They were set on supports ready for demolition at a later date, and the same SPMT was then used to pick up and transport the new bridge, a single span ‘U’ deck carrying one track only, complete with pre cast concrete cill units attached, onto the road ready for installation. Following abutment lowering and installation of a levelling screed, the new bridge was moved and set in its final position on Christmas morning. Deck end drainage was then installed before backfilling and bottom ballast was placed. The existing track was then reinstalled, and all work was completed on programme well within the planned constraints of the blockade. 

  • Installation of under track crossings and diversion of S&T cables onto the side of the railway where the new bridge was to be installed.
  • Erection of temporary scaffold bridge to support S & T cables which were moved out of the way of the works prior to the main possession.
  • Removal and storage of track superstructure.
  • Safe removal of 110 year old 50 Tonne structure to site compound using Self Propelled Mobile Transporters (SPMTs).
  • Reduction of abutments and installation of screed to accommodate new pre-cast concrete cill units.
  • Transport and installation of new bridge using SPMTs, complete with cill units, total weight 200 Tonnes.
  • New ballast retention units installed on the approaches to the new structure.
  • Reinstallation of track superstructure.
  • Face riser units with brickwork to match the existing abutments.

Successes

  • Works completed on programme, within the constraints of the blockade.
  • Shallower bridge construction depth allowed a headroom increase of approximately 140mm for road vehicles.
  • Passive provision for the installation of an additional bridge should the line be returned to twin track operation in the future.
  • New access staircase provided at the site of the bridge allowing good access for railway staff to track level.
  • New bridge complies with Network Rail collision management status ‘Double Amber’ which has much less impact on the operational railway in the event of a vehicle striking the bridge.