The British Geotechnical Association (BGA) is the principal association for geotechnical engineers in the UK.
The Geotechnical Engineering Proceedings Lecture is a biennial lecture nominated by the Editorial Panel of ICE Proceedings Geotechnical Engineering.
This event is planned as an in-person event, and will also be webcast live.
This event is free to attend.
Advance booking is required for both in-person attendance and on-line viewing, via the booking link.
The British Geotechnical Association
04.11.2026
18:00 - 20:30
Insititution of Civil Engineers, One Great George Street, London
This event is free to attend. Advance booking is required for this event.
BGA Event
Refreshments will be available from 30 minutes before the start of the lecture. After the lecture networking will continue at a reception with alcoholic and non-alcoholic beverages available.
This paper describes the installation and interpretation of strain gauges embedded in the sprayed concrete lining of the concourse tunnel at Heathrow Terminal 4 station, with readings taken over nearly 20 years. The rate of flow method was used to back-calculate stresses from the measured strains, which were then compared with the stresses obtained from pressure cells at the same locations. The resulting 20-year history of stress and strain gives precious insights into the short- and long-term behaviour of a sprayed concrete lining. An increase in compressive strain up to 3 years followed by a slight decrease over the subsequent 15–16 years has been revealed. It is hypothesised that this is due to radial groundwater flow through the primary lining followed by the gradual application of hydrostatic water pressure to the waterproof membrane and secondary lining.
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