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The original bentonite shield
The first bentonite tunnelling machine based on John Bartlett’s patent was 4m in diameter, 4m long and weighed 70t. It was manufactured by Robert L Priestley Ltd.
Image credit : Mann Brothers
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Recognising our innovations in tunnelling with the 60th anniversary of the bentonite shield patent

Mott, Hay & Anderson chairman John Bartlett’s invention of the bentonite shield revolutionised tunnelling in poor ground making it safer and more cost effective.

Mott MacDonald has been enabling tunnelling breakthroughs since the work of founders Basil Mott and David Hay in the 1890s. In 1964 John Bartlett followed in their pioneering footsteps by inventing a new methodology for tunnelling in non-cohesive, water bearing soils that were prone to collapse during excavation.

Hear the full story in our latest podcast.

These conditions although very common were considered too dangerous for underground construction. Tunnels were designed to avoid silts, sands and gravels, where there was a risk of water ingress and a high potential for failure. John Bartlett’s invention changed that because it introduced the use of bentonite slurry to pressurise and support the face of tunnels during excavation.

“John really cared about how to make tunnelling safer and more affordable and his invention really captured the essence of what was needed,” says Mike Saville, global practice leader for tunnelling. “It led to the notion that tunnelling was now for the masses, and the subsequent explosion in the amount of tunnelling around the world in Asia and Europe speaks to that.”

The podcast tells the story of how the bentonite tunnel boring machine was tested beneath the city of London in 1971. John Bartlett’s son Mike sheds light on the inventive and generous man who went around the world 40 times to share his knowledge. Finally engineers from across the business explain how this spirit of innovation is driving us to successfully design tunnels that would not have been possible without pressurised face machines such as the Storebaelt Tunnel in Denmark, the Channel Tunnel between England and France, and the East Side Access project in New York.

Featuring global practice leader for tunnelling Mike Saville, head of tunnel design for the US eastern region Andy Thompson, tunnelling engineer Emily Farmer and principal structural engineer for tunnels Sam Lo Grasso.

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