The use of jacked-box tunnelling under a live motorway

Jacked-box tunnelling is a non-invasive technique for constructing a new underpass, culvert or subway beneath existing infrastructure, such as highways and railways. It was used for the first time under a live motorway in the United Kingdom at junction 15A, on the MI motorway, when a vehicular underpass 14 m wide and 8·2 m high by 45 m long was installed with 1·6 m minimum cover to the motorway. The paper describes the technique, and how it was applied in the design and construction of this innovative project. Particular attention is given to the ground movement control measures adopted, which made it possible to safely install a large monolithic box structure at shallow depth beneath the motorway without impeding motorway traffic.