Holdfast Training Services Trial Blog

At the end of the second week I find myself in a similar situation to Ryan as I too am now fully immersed in Cross Rail although we have yet to truly establish who’s shaft is truly bigger.

I am attached to Lain O’Rourke team working on the C502 Contract which is the construction of the Liverpool Street Station ventilation and services shaft at present but is due to expand to include the Liverpool Street and Moorgate Cross rail ticket halls in the near future. I will not repeat Ryan’s intro to the Cross Rail act but would refer you to his last blog if you are interested.

The Liverpool Street Station ventilation shaft is a top down build comprising of 12 levels over a depth of 52 metres. The shafts purpose is to provided ventilation, maintenance access to platforms for E&M services and to act as emergency access and egress from the Cross Rail tunnels.

At time of arriving on site all piling work has been completed and the capping beam had been cast. A working surface for the first mass concrete pour had been constructed and the steel fixers and carpenters were commencing fitting of the first reinforcement cages in preparation for the pouring of the first slab of the main build.

Following a comprehensive week of induction and Health and Safety last week I have finally been set to work and given the responsibility for rebar detailing for the future slabs, columns and beams as the project progresses. Key to this role is a clear understanding of the construction sequence and understanding how the various structural elements of the shaft will be tied together. Neither of which I am fully up to speed with just yet….some more reading required.

In addition I have been made responsible for a temporary shaft from which another Cross Rail will injection grout in order to stabilise the ground for tunnels that will run next to the site. At time of arrival the main slab had been poured and the excavation beneath the slab had almost been completed. First task has been to break out the concrete in the piles to find the couplers from which the bottom slab rebar will be connected. The couplers were put in place with the reinforcement cage through a bentanite slurry and then concrete poured to form the piles. It was not a surprise to discover that some of the couplers were either missing in action or misaligned. For these the concrete piles have been drilled and rebar starter bars have been resin fixed into the piles. Begs the question why not drill and resin fix all starter bars to avoid breaking out the concrete piles….answers on a post card.