For those outside the UK, the Crossrail project is a mega-project upgrade to the London metro area’s subway system. The tunneling portion of the project will consist of 21-km of twin-bore tunnels excavated by eight closed-faced tunnel boring machines, six of which will be earth pressure balance machines (EPBMs). The UK’s Geological Society has published an interesting article on the geology of the crossrail project. Some of the geological and geotechnical challenges of the project include the famous London Clay, sensitive structures, faults, and rapid transitions between permeable and relatively impermeable formations creating potential water pressure issues. [Source: Geological Society. Image: Geological Society]
