Apacked house was present for the BTS evening meeting by Chappell, Harding and King on the design of Concrete Lining for Tunnels at the Institution of Civil Engineers. Roger Bridge, BTS Chairman, introduced the three speakers: Mike King is currently Head of Underground Construction on Crossrail, Anthony Harding is Global Technical Leader for Tunnels at CH2M and Malcolm Chappell is a consultant and director of Ozengi, and was CH2M’s Director for Tunnelling in the Pacific region with extensive experience from both sides of the fence in terms of contracting and consulting.
The meeting was set around their paper ‘Continuing innovation in segmentally lined tunnels, and Malcolm started by noting that in the last 40 years the tunnelling industry had seen significant changes in technologies in TBM tunnelling and segmental linings through a range of interesting case histories. He outlined the developments achieved in 40 years and then prompted possible future developments in concrete linings, geopolymer concrete, fibre reinforcement, intelligent segments and energy segments and the trend towards larger diameter tunnels and therefore larger segments.
Anthony then took over to put some technical information behind these ideas. He discussed plain concrete, aspects rations and the various load cases that are considered in terms of handling and the like when considering the need for reinforcement within the lining. He outlined the use of geopolymer, testing and their current use in schemes being limited to date. Anthony attempted to be persuasive on their performance and benefits referring to cost. This enthusiasm was held back by the lack of mature supply chains currently. He went onto to cover macro synthetic fibres and eventually the reduction and possible elimination of the use of bolts in tunnel lining. This would assist with an easier installation and corresponding reduction in TBM crew sizes. He also described the issue of "intelligent structures" that monitor performance automatically to assist when maintenance is required. He went on to elaborate on energy recovery systems built into the lining and concluded with further thoughts on future trends in larger tunnel and segment sizes.
Mike then continued with an opening stating that he wished to promote debate without having all the answers with a series of quotes and prompts set around a number of sources including Tony Blair and Margaret Thatcher. He discussed what enables innovation and the awareness of its importance as well as an appreciation of the cost to avoid British Tunnelling lagging behind the rest of the world. He described the need for Technical Peer Review to give confidence in the industry and suggested the need for a group to lead on Tunnelling and Innovation to ensure this remains in the fore. He ended by saying that the tunnelling industry has the ability to manage the risks and ensure that improvements to segmental linings continue at the same pace as they have in the last decade.
The Chair then took control of an active Question and Answer session with subjects such as who owns the cement industry through to the use of tunnel linings without reinforcement being common practice in the past. Comparisons were made with Sprayed Concrete Tunnel lining and the traditional methods of timber headings and SGI linings from a number of experienced tunnel engineers in the room. The Chair drew the meeting to a close with the traditional applause, thanking the speakers for their presentation and no doubt further discussion ensued in the institution’s bar afterwards
