TECHNICAL | BTS, LINING – SLIPFORMING
SLIPFORM TUNNELLING
The potential for slipform technology in tunnelling was described by Prof Colin M. Eddie and Dr. Henry Pairaudeau of CECL Global Ltd at the BTS evening meeting in December 2025.
INTRODUCTION In 2006, for the Sir Harold Harding Memorial Lecture, Professor Colin Eddie discussed the future of tunnelling technologies, including the potential for slipform systems to create structural linings for bored tunnels. In December 2025, he briefed the BTS on the latest work in the area, focused on his own research work along with co-presenter Dr. Henry Pairaudeau. Their concept is to excavate by TBM while continuously and simultaneously slipforming the lining, and it builds upon five years of research and development work to create the ‘Slipform Tunnelling’ system (trademarked). It is patented by CECL-Global, which they work for, and along with a consortium of partners – Robbins, UGITEC, Bekaert and Master Builders – the aim is to bring the system to market.
HISTORY Noting that he has been “banging on about extruded linings for a long time,” Colin said government would not fund research and he ended up backing it himself, equivalent to about 20% of CECL’s turnover, or 40% of profits, has been spent on the research. CECL is invested in it. Marc Brunel, inventor of the first tunnelling shield,
observed the shipworm, Teredo Navalis, boring through timber at Chatham Dockyard. While the inspiration gave rise to the shield for the first Thames Tunnel and he did wonder about extrusion, there was no such lining developed as a result. Recent research learned that efforts at extrusion were
Figure 1.
The Slipform Tunnelling system, in Synchronous arrangement for
constructing new tunnels.
made in the USSR in the 1960s, pumping concrete into an annular gap between a demountable, segmental ‘jump’ shutter and the excavated ground profile. But they only had normal concrete without admixtures, and with that shutter there was no benefit to the industry compared to segmental lining, Colin said. Still, he noted that the Russians were the first.
“A serious piece of research that wasn’t well publicised”,
was undertaken in the US, in the 1970s/80s, by Foster Miller. The Extruded Lining System was “truly a slipform shutter” and was used in combination with a gripper shield “but again they were trying to make accelerated concrete work,” he said. Large-scale laboratory tests were performed but issues with logistics, quality and system complexity meant it was never trialled on a live project. While “many good things came out of this” in the end it did not work and was of no benefit to the industry, he said. In the 1980s, Hochtief spent “considerable time and effort”
looking at extruded linings. A number of projects were built but they were not the most efficient, he said. Relatively recently, Extruded Concrete Lining (ECL)
systems have been used in Japan. “But again, we’ve got shutters that were being disassembled and moved to the front,” he said, which again does not improve upon just building segmental rings. He also mentioned the Brazilian Borer (‘BraBo’) system, which would use accelerated concrete but, he believes, did not get off the drawing board. Another recent push in extrusion lining systems is in Italy, for tunnel repairs, involving the Hinfra shutter system and pumped fibre concrete. Benefiting the industry “is a key issue,” he added.
INNOVATIONS Undertaking a fundamental rethink on how to look at extruded linings, Colin has worked with colleagues to develop a new approach – an ‘instant structural lining’ – and the new mechanised system involved is not reliant upon any chemical process or hydration of cement, he said. To place the one-pass, mechanically pressed lining, two
different versions of the mechanised system have been in development: Synchronous; and Non-Synchronous.
Synchronous The Synchronous system is for construction of new tunnels. It involves placing the slipformed lining immediately behind the excavation performed by either TBM or open-face shield (e.g. by back-hoe or roadheader). It is to be applicable for different profiles (incl. non- circular). Advance rates are too unconstrained by the lining process as it will be fast enough to match the excavation rate of any machine. For the Synchronous mode it employs a ring of injectors, positioned around the periphery of the shield tail/shutter connection. Each injector is aligned to the tunnel axis and will feed a specially developed lining material between the shutter and ground profile.
Non-Synchronous The Non-Synchronous system is not meant for use in building new tunnels but for relining existing tunnels
10 | October 2026
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