LEADING INTERNATIONAL geotechnical engineers are warning against the danger of using too wide a range of instrumentation in soft-ground tunnels built with sprayed concrete temporary linings.
The warning comes in the lead paper of the current issue of the ICE journal Geotechnical Engineering (volume 143,3), and follows the high-profile collapses of such tunnels in Munich, Sao Paulo and Heathrow Airport in Britain.
Professor Chris Clayton of the University of Southampton and colleagues from the UK, South Africa and Brazil recommend that a small number of reliable and well-understood monitoring techniques should be used to monitor the lining performance.
A proliferation of diverse apparatus can be counter-productive, they say, diverting focus from reliable techniques and overloading data management systems.
According to the authors, core measurements on a sprayed concrete lined tunnel project should be convergence, using total stations and tape extensometers; pressure, using boundary pressure cells; and displacement, using precise levelling, inclinometers, chain deflectometers and electrolevels.
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