Rock Me Amadeus

28 February 2013

NATM is a frequently misunderstood approach to tunnelling. Its deĀ¬ nition, its use and its advantages are often the subject of debate. In this issue of Tunnels, Austrian Society for Geomechanics (OeGG) president Wulf Schubert attempts to tackle the issue.

Fifty years of NATM were celebrated at the Geomechanics Colloquium in Salzburg last October as the OeGG welcomed the industry to its 61st event.

The International Society of Rock Mechanics was founded in Salzburg that May in 1962. And at that year's colloquium, Professor Rabcewicz coined the phrase 'New Austrian Tunnelling Method' (NATM).

It was the first visit to the show by the current Tunnels team, following recommendations, invitations and coercion by engineers from within Austria and abroad. And it didn't disappoint. Gone were the too often tepid offerings of the usual conference lecture sessions, as the first round of presentations brought together speakers from around the world to explore regional evolutions of NATM.

Mercifully, the planned use of underground space was only hinted at as a topic. The highlight was the opening session on regional NATM developments. As chair, Wulf Schubert mentions the 'occasional attacks' on the method that have not prevented its adoption around the world in some of the most difficult geological conditions.

To someone familiar with British tunnelling history, the Heathrow Collapse stands out, and is brought up in the British offering to the regional session by David Hindle and Maurice Gooderham. They state that as a result of the collapse, all NATM work in the UK was suspended, and an ICE commission decided that in soft ground it was not possible to use the NATM philosophy of mobilising inherent ground strength through deformation. Resulting HSE publications have had a damning effect on NATM in the UK to this day.

A challenge is laid down in the conference - for more engineers to come and present their country's ideas on NATM in front of a vocal audience. As for British attendance at the 2012 colloquium, the three-strong contingent (including Tunnels) is telling.

The comment written by Hindle previewed his and Gooderham's presentation, and asked 'what is SCL?' For although NATM is a sprayed concrete method, it has completely different implications to the British 'Sprayed Concrete Lining' design concept which attracts such amusement in Austria for its conservative approach. British engineers in particular are invited to present their views on the sequential approach in future colloquiums.

Perhaps the paper presented by Schubert will help with some of the confusion, as even the ITA president is told after his presentation that many of his examples are not truly NATM. Schubert tells Tunnels that his hope is to end the mysticism surrounding tunnelling and for it to be seen as a regular engineering task.

See you there this year