Fisher Street Shaft

The Fisher Street Shaft site was the service access shaft for the Crossrail C300 tunnel drive from Royal Oak to Farringdon, but was limited to an area of 20m by 20m restricting the available plant which could access and operate on the site.

Martello were able to place two MP5000 series rigs AND a crawler crane within the site constraints to enable maximum output to be achieved. The programme was achieved on time allowing the main contractor to complete their works without delay, lessening the risk of very costly delays to the tunnel boring machine.

The MP5000 series rigs were able to install the piled wall to a verticality of 1 in 200 (or better).

The compact nature of the rigs allowed the operations to be undertaken with multiple rigs, done safely within a busy and constricted area of London.

The works involved the installation of a 17.5m diameter shaft from which the Crossrail TBM could be serviced.

The project required a 600mm secant wall to 14m depth to form the upper shaft through unstable material. Below this depth the rest of the shaft was undertaken using a sprayed concrete lining.

Foam concrete was used as a void filler which surpassed the specified strength by ten times. Our MP5000 series rig was able to bore through this without a delay in programme.

This type of shaft construction can be utilised on other constrained sites to achieve large diameter shafts.