Delivering the Moorgate shaft base slab on Crossrail, UK

The Moorgate shaft at Crossrail Liverpool Street station is one of the deepest in London, UK. Construction of the base slab to the 42 m deep shaft required close collaboration between the client, designer, contractor and suppliers to give assurance that the slab was watertight. Dense reinforcement was detailed to ensure ease of fixing within the tight confines of the shaft and allow for the tolerance on the diaphragm walls. The concrete design was developed to ensure that it met the requirements for placing and structural strength while achieving good control on the temperature developed. The concrete mix was trialled for temperature development and initial set to allow relaxation of the original specification. The pour plan was developed with the co-operation of all the site teams to ensure appropriate contingency measures were in place. Temperature monitoring was carried out to ensure that mitigation measures could be applied to control placed concrete temperature against predetermined trigger levels.