Tunnel boring machine Emma
The tunnel boring machine Emma was built to bore the Duplex A86, a 10.1 kilometres (6.3 mi) tunneled section of the A86 autoroute.[1] She was 11.56 metres (37.9 ft) in diameter.
Emma was designed so its cutting head could switch from boring through rock, to boring through water-logged soil.[1] To bore through water-logged soil the area around Emma's business end, the cutting heads, was pressurized with a Bentonite slurry.[2] The Bentonite slurry was a kind of muddy paste, and by keeping it pressurized, it prevented the soggy soil from trying to squirt into the cutter.
It took Emma's crew one week to switch the cutting head from hard rock to water-logged soil.[2]
References
[edit | edit source]- ↑ 1.0 1.1 "The A86 double-deck tunnel - An exceptional engineering feat". Geotechnique. 2011-01-09. Retrieved 2025-03-05.
- ↑ 2.0 2.1
Ed Owen (2007-01-18). "Emma and the Parisians". New Civil Engineer. Retrieved 2025-03-05.
In the TBM's control room, noise is reduced to a loud squeal. 'We are travelling at 43mm per minute, ' he announces. 'It is possible to go off-course if there are unexpected changes in the geology, but this is never more than a few centimetres.' Local geology does vary, and the TBM has been adapted to deal with both hard and soft ground. It is an earth pressure balance machine with bentonite injection used to lubricate the and ease spoil removal. Rock spoil is removed from the cutting face using a screw conveyor.