A new technique of sprayed concrete is to be tested during the Bond Street Station Upgrade (BSSU) project in a joint venture (JV) between Costain and Laing O'Rourke.

The JV is the first partnership in the world to test the method in a production environment.

By using a thermal imaging camera to track the temperature of concrete forming the tunnel lining, this allows engineers to calculate the amount of hydration that has taken place in the concrete, and hence its strength.

The Strength Monitoring Using Thermal Imaging (SMUTI) method has been invented by Dr Benoit Jones from Cambridge University.

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Aled Davies, Costain Senior Tunnel Engineer, who has worked closely with Dr Jones on the trials, said SMUTI is a "significant step forward for health and safety".

"SMUTI allows us to directly monitor the compressive strength development of sprayed concrete whilst remaining at a safe distance," he said.

"This is a substantial improvement over the current method, which relies upon a small test panel being representative of the entire sprayed concrete advance to prevent personnel being at risk from sprayed concrete lining falls."

Mr Davies added: "The trials have gone very well and the workforce was very appreciative of the time and efforts being taken to improve their safety.

"The data is now being analysed but we hope to have the results by September, when we will present them to tunnelling sector clients and design partners."

(LM/CD)