The paper has shown that the starting point for a jacked box tunnelling project is a detailed understanding of the ground conditions and geotechnical parameters to be used in the design of the tunnelling system and permanent works. Ideally, these requirements should be achieved through an early involvement and close working relationship between the jacked box tunnelling engineer and a suitably qualified geotechnical engineer. The greater the confidence the jacked box tunnelling engineer has in the ground conditions and the geotechnical parameters, the more efficient the installation becomes. A high level of confidence made it possible to install the rail tunnel at Lewisham Station with 1.7m of cover, and the underbridge at Junction 15A of the Ml motorway with 1.6m of minimum cover. Similarly in Boston, USA, confidence in the geotechnical behaviour of frozen ground made it possible to install the longest jacked box tunnels in the world to date. Based on their experience, the authors believe that the unique and non-invasive technique of jacked box tunnelling will be used widely in the future to install even larger boxes through a greater variety of ground conditions.
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