As part of the Metropolitan Line bridge maintenance scheme Gobion Construction were appointed by Loftus Group to demolish bridge MR2, a disused bridge spanning the North and South line near Baker St Station, and construct a reinforced collision impact wall at street level.
This scope of works was phased over a 18 weeks period which involved the controlled dismantling of the bridge and centre pier, installation of 14no. piles at 10m depth, construction of a reinforced retaining wall at street level. We designed and installed our own temporary works for both access and as a crash deck for demolition works. We also designed lift plans for cranes and excavators to carry out the lifting of the precast bridge deck and demolition risings from track level to skips at street level. Demolition works were carried out in both engineering hours and on possessions. The bridge structure was successfully dismantled 2 weeks ahead of programme and without any late delays to the train service.
Once the bridge was demolished, we designed complex temporary works for the abutment supports which enabled us to carry out piling during traffic hours with some of the piles being only 300mm away from the envelope of the passing trains. We were very pleased to have achieved this as it was the first time this had been carried out on an LU project.
Following the successful piling works, we constructed a reinforced retaining wall on top of the abutment wall. This work was carried in both traffic and engineering hours. We installed the trackside shutters first on engineering hours to create a solid screen, this enabled the steelfixing and the rest of the shuttering work to be carried out in traffic hours. Once the wall was tied we poured the concrete via pump on engineering hours. This was done very successfully with no disruption to service. To finish off the wall we constructed a brick façade on the street side to blend in with the surrounding structures. We also laid a new path and decorative bollards.