The only thing we have to fear...

4 June 2012

Some 60m under Zhanjiang Bay in southern China, and about a kilometer from the tunnel entrance, this editor breaks for water with the project manager and the chief engineer.

Together we are walking the four per cent slope down to the TBM cutting the water transfer tunnel. The tunnel is pristine. It is lined with smooth concrete segments, gasketed and sealed with a coating of mortar to hold back the six bar of water pressure bearing down on the tunnel.

The ventilation system hums as it battles to keep the tunnel cool. With outside air temperatures creeping above 30°C the tunnel can quickly become stiflingly hot.

As we continue to march down the tunnel, the journey is cut short by the sound of rushing water and a thunderous slapping of the severed ventilation line. Elevated on a walkway above the tunnel invert mud quickly begins to flow beneath our feet.

Instinctively, the video camera is set rolling and homes in on the source of the inflow of liquid mud half a kilometer upstream. As many of you will have just done, this editor leapt to the conclusion that he was witnessing the result of poor design and construction of a Chinese tunnel. Perhaps expecting it to be the last thing he witnesses. In fact, the flow of mud, the ruptured ventilation line and the panic was the result of a failed coupling on the exiting slurry line. We were never in any real danger.

This not-so-near-death experience highlights a major challenge for the industry as a whole in tackling the perception of tunnelling and its dangers.

It is evident - not least by two stories in the news this month, a blast killing 20 in a tunnel in China and an explosion killing four in a tunnel in Japan - that tunnelling is a dangerous business. But with an estimated 500 TBMs currently in operation in China and a presently immeasurable number of tunnelling projects, it is clearly unfair to judge an industry on one-off or rare occurrences.

The Zhanjiang project is being carried out to an international standard; we will be giving a full report in the near future. It was preconceptions of China's tunnelling that spurred the fear in the tunnel. Everything about the project looked to be carried out with utmost integrity.

On page 6 of this issue we report on a scare mongering video released by the Parent Teachers Association in objection to the construction of a metro line under a school in Beverly Hills, USA. The film grossly exaggerates the real dangers of tunnelling and invents a series of new ones in an attempt to halt the project. In our sister publication T&T North America, managing editor Nicole Robinson gets her teeth into the issue, it is well worth a read.

As members of the tunnelling fraternity it is our role to present the industry positively and accurately to the general public, and the first step is understanding the actual ability of our colleagues, near or far, and not the perceived ability.

Safe digging!

By Jon Young