Award for British inventor of slurry TBM concept 04 Oct 2018

Without the ingenuity of British inventor and engineer John Bartlett CBE FREng tunnel boring might work very differently to how it does today.

As inventor of prototype soft ground pressurised TBM technology, Bartlett has been recognised by the Royal Academy of Engineering with its highest accolades, the Sir Frank Whittle Medal.

Bartlett patented his bentonite tunnelling machine in 1964 and it became the forebear to today’s pressurised TBMs and the first machine to enable the excavation of non-cohesive soils safely, efficiently and on a grand scale.

The impact of his ingenuity on the tunnelling world has been recognised by industry giants the world over and he has received many awards and accolades for his career contribution to tunnel engineering, including a CBE (Commander of the Most Excellent Order of the British Empire) from Her Royal Highness Queen Elizabeth II in 1976 and the James Clark Medal from the British Tunnelling Society in 1994.

In a congratulatory letter to Bartlett, current BTS Chair Ivor Thomas wrote: “Your invention of the slurry machine and its subsequent development has made a tremendous difference to how and where we can tunnel. Slurry tunnelling has allowed us to develop tunnels in geology that would previously have been either very difficult and costly or impossible. Much of the Jubilee Line to the south of the River, the Channel Tunnel Rail Link Crossing and the Crossrail River Crossing were only made possible by the use of slurry machines.”

Lord Robert Mair CBE FREng FRS, President of the Institution of Civil Engineers, echoed the sentiments surmising: “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.”

Born in 1927, career work by Bartlett over the last six decades has transformed tunnelling technology. Boring tunnels in non-cohesive soils - sands, silts, gravels and mixed ground - requires continuous support and control of ground water content. Compressed air allowed hand-mining excavation in such loose soils, but it was the invention of the bentonite tunnelling machine that superseded these hazardous and expensive operations.

Inspired by a visit to Milan, Bartlett observed how the city’s first metro line had been built using the cut-and-cover method using bentonite clay to support the trenches, the thick thixotropic gel at rest, becomes a bentonite clay slurry when agitated. Bartlett's concept was to combined slurry support of trenches with mechanical excavation.

The result was the Bentonite Tunnelling Machine. 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.

The BTM 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. Bartlett designed and supervised construction of the first, experimental, BTM tunnelling contract in southeast London in 1971. In 1973, he was awarded the Royal Society’s SG Brown Medal for the invention of the BTM.

The pride in Bartlett’s invention and career is still felt today current BTS Chair Ivor Thomas noted: “The company I work for, Bam Nuttall are sister company to Wayss & Freytag and I take great joy in pointing out the British history of the Bentonite Machine when my German colleagues have the temerity to mention their invention! In the last year we have had three slurry machines in the ground. The drives would have been a lot harder to say probably impossible with the old compressed air techniques.”

Bartlett’s machine’s descendants have been used in many major civil engineering projects including Ada and Phyllis, 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’.

Among his many other achievements Bartlett designed the UK side of the Channel Tunnel. He 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.

Bartlett spent most of his career with consulting engineers Mott Hay & Anderson from 1957 until his retirement as Chairman and Senior Partner in 1988 having overseen the firm’s transformation from a small London consultancy to worldwide success with major projects in five continents, and having led the merger talks that led to the formation of Mott MacDonald in 1989, now one of Britain’s leading firms of consulting engineers.

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 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 between 1977 and 1979 and was President of the Institution of Civil Engineers in 1982. Barlett has also written several papers and books on engineering science, notably Tunnels: Planning, Design, Construction Volumes 1 and 2.

On receiving the award, Bartlett said: “Civil Engineering today is a team game. I hope members of my team will enjoy sharing the recognition given by this award. Many thanks to those who put me forward.”

Lord Robert Mair CBE FREng FRS, President of the Institution of Civil Engineers, said: “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.”