Moorgate Shaft Base Slab, design, detailing and construction
Summary
The Moorgate shaft at Crossrail Liverpool Street station is one of the deepest in London. Construction of the base slab to the 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 whilst 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 cooperation 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 pre-determined trigger levels.