The removal of the last level crossing on the West Coast Main Line is now well underway after the successful installation of a Box-Jacked undepass in Tipton last weeked.
BAM Nuttall installed the 6,500t concrete box without hitch over the Easter weekend, handing back possession of the railway to Network Rail two and a half hours early.
Over the weekend 250 people were used to shift 6,500m³ of muck and inject 23m³ (or 28t) of grout.
Sandwell Metropolitan Borough Council first started trying to get rid of the crossing in the 1950s. It is believed to be the last such crossing on the West Coast Main Line (WCML) and its road barriers are down for an incredible 45 minutes in every hour as a succession of high speed and local commuter trains whip by. This is hardly ideal for encouraging business into Tipton.
A 101 hour possession started on Good Friday and the jack had to be finished when it ended on Easter Monday. As a result the box had to march forward at 2.5m to 3m an hour.
As soon as the overhead power lines are turned off, workers sprang into action: track was lifted, ballast removed, and excavators moved into position to start digging out ahead of the box. The box was driven along by three jacks, each connected top and bottom to its rear end. Pretressed Macalloy bars held the jacks in place at the top, each carrying 91t of load.
Despite the need for speed, care and precision was required as the overhead catenaries and cables remained in place. Lubrication was also all important. Steel ropes were fed along the underside of the box to help it slide, with four “treads” each with 128 ropes.
In addition, bentonite was injected along the sides of the box through nozzles between the box wall and the excavated face. After jacking was complete, the bentonite was expelled with grout, which also fixed the box in place.