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Comment | Underground construction just keeps on getting better

Alexandra Wynne

Society is increasingly demanding underground space to meet its needs and the civil engineering profession is increasingly responding to that need.

That’s been evident this month as the engineering world marks another great feat with the opening of the world’s longest rail tunnel – the Swiss Gotthard Base Tunnel.

“This is a huge engineering achievement,” proclaimed ICE fellow and CH2M Tunnels and Earth Engineering Practice managing director Martin Knights as the 57km long tunnel was unveiled after a 17 year construction programme. He’s quite right. It is a huge achievement, and one that is sure to be bettered again as the industry continues to advance.

And it needs to: because despite the obvious prestige granted to those tunnellers working on the world record beating projects it is not just vanity pushing them to go where no person has gone before. There is a simple pragmatic reason behind it all.

Space above ground is at a premium. There may be some who are a little sick of the word urbanisation and how often it is trotted out by economists, politicians and self-proclaimed futurists.

Amid the jargon lies a great global engineering challenge: How to provide vital and safe water, energy and transport systems with so many people congregating in metropolitan squalls. The United Nations predictions suggest that by 2050 the proportion of the world’s population living an urban life will increase to 66%, up from 54% in 2014.

A good number will need to be accommodated in already congested cities.

Making use of the earth beneath us will become increasingly important in terms of transport and energy infrastructure.

Singapore has firmly grasped this point of view. It is the third most densely populated country in the world and covers just 717km2.

So last year, the country introduced an edict to ensure state ownership of land below 30m depths. The edict provides for private basement construction and deep piling but otherwise the land is available for the government to free up precious overground space for housing, parks and recreation by taking transport and energy systems well below ground.

The country does urbanisation in a way that many may seek to emulate. While its CO2 emissions are currently well above average for OECD countries, they are now falling.

Governments and investors are waking up to offsetting the sometimes eye watering upfront costs of major tunnelling projects with the social and environmental benefits that the end product will bring. But tunnelling often remains a high risk endeavour.

The up to 11 bar pressure encountered 106m below sea level on the Eurasia Tunnel in Istanbul, alongside nervousness about high profile tunnel boring machine (TBM) problems – such as those that hit a Hitachi Zosen machine on the Alaskan highway in Seattle – put huge pressure on those involved.

Contractor Yapı Merkezi board member Basar Arıoglu told New Civil Engineer earlier this year that that pressure was coming from all angles, even from the boss of tunnel boring machine giant Herrenknecht: “Martin Herrenknecht was telling me, if this project has a problem like the one in America, then you can forget about the big TBMs for a while because nobody will insure them.” 

And then there is the ongoing challenge around tunnelling safety. In 2004, Singapore witnessed one of the most memorable fatal accidents in construction when the diaphragm walls of an open cut tunnel being excavated for Singapore Mass Rapid Transit’s Circle Line caved in, killing four construction workers.

While Gotthard is a technical engineering success, nine workers died during its 17 year construction. 

London’s mega tunnelling project Crossrail has also failed to complete its work without blemish – while the 2014 death of Rene Tkacik was ruled an accident by the coroner, he was killed while undertaking concrete spraying operations.

As London tunnelling expertise moves on to that other mega-project – the 25km long Tideway tunnel – there is a desire to try and improve things when it comes to safety.

As we learn from the special supplement with this month’s New Civil Engineer, Tideway is using the word transformational.

Its EPIC safety induction is designed to be impactful and no-one – according to Tideway chief executive Andy Mitchell – is getting near one of its sites without having done the full one day induction – not even to change a lightbulb or fit a new filter on a crane.

The consequences when anything goes wrong in tunnelling appear multiplied, which demands that ever newer, better design, techniques, methods, people, equipment and technology are used.

Only then, and perhaps when robots are truly competent and reliable to take over, will the real potential of going deeper, longer and wider underground be fully realised.

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