24 Nov, 2021 By Claire Smith
Former ICE president and tunnelling specialist John Bartlett, who recently died, was probably best known for his work on the Channel Tunnel. However, his work over the last six decades transformed tunnelling technology with the invention of the bentonite tunnelling machine for work in loose and sandy soils.
Despite Bartlett’s career focusing on civil engineering, he had degrees in both law and civil engineering and continued to study for his bar exams even after joining contractor John Mowlem. He soon decided to focus in civils and Bartlett spent most of his career with consulting engineers Mott Hay and Anderson and worked there from 1957 until his retirement as chairman and senior partner in 1988.
He worked on the first Dartford Tunnel, the first tunnelled sections of the Toronto Subway and was the project engineer responsible for London’s Victoria Line. He also had design responsibility for the Channel Tunnel, first as principal designer for the scheme and following the project’s revision in the early 1970s, as principal design consultant for all civil and geotechnical engineering on the UK section.
He was elected a fellow of the Fellowship (now the Royal Academy) of Engineering in 1978 and was a founder member and Chair of the British Tunnelling Society. In 1982 he was elected president of the ICE.
In 2018, Bartlett was presented with the Sir Frank Whittle Medal, which is awarded to an engineer whose sustained achievements have had a profound impact upon their engineering discipline, by the Royal Academy for Engineering. At the award ceremony, Bartlett said: “Civil Engineering today is a team game. I hope members of my team will enjoy sharing the recognition given by this award.”
Speaking at the time of the award, then ICE president Lord Robert Mair told NCE’s sister title GE: “There can be no doubt that a major revolution in the worldwide tunnelling industry was triggered by John Bartlett’s invention of the bentonite tunnelling machine. It has enabled a rapid increase in tunnel construction around the world, particularly in urban areas, for water supply, sanitation and transport – with remarkable benefit to humanity.”
Bartlett’s solution was inspired by a visit to Milan, where he observed how the city’s first metro line had been built using a cut and cover method rather than bored tunnels. The engineers had used bentonite clay to support the trenches while they were being excavated. Bartlett began developing a new type of tunnelling machine that combined slurry trenches with mechanical digging technology.
The result was the bentonite tunnelling machine, which he patented in 1964. The machine uses pressurised bentonite slurry in a sealed bulkhead behind the cutting face to balance the water pressure in the ground and stabilise the tunnel while supporting rings are installed. The excavated soil is then separated from the slurry, which is recirculated to the cutting face.
Bartlett’s bentonite tunnelling machine became the prototype for a whole new class of slurry tunnelling machines and by the end of the 1970s more than 1,000 had been used worldwide. The machine’s descendants have been used in many major civil engineering projects. They include Sophia and Mary, the giant boring machines used by Crossrail to construct tunnels between Royal Oak and Farringdon, and Busy Lizzie, which was used to cut the Lee Tunnel, the first section of London’s Thames Tideway super sewer.
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Of course we already have Dinorwig here in the UK but I am surprised more pumped storage schemes are not being considered as a way to extend wind and solar power availability and reduce our dependence on natural gas to ‘fill the gap’ in electricity generation.
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