Quo vadis NATM as seen by the designer / Quo vadis NÖT aus Sicht des Planers

The first NATM designs 40 years ago included only one plan with the tender documents, the so-called support measures plan with five to six rock quality classes and at the most 30 to 40 bill items and perhaps just 20 pages of technical conditions of contract. The tunnelling work on site was mostly implemented collaboratively, quickly and according to the requirements of the client. The main advantage of the NATM, its adaptability, could be exploited to the full. Meanwhile, the extent of the tender documents has increased by a factor of more than ten. Does the NATM have less economic risk and less conflict potential as a result of this? No! The only progress is that tunnelling has become safer. The reason for the exploding quantity of design and tender documents is not that the technical requirements and their solution have become more extensive but in the immense increase of legal influence and the resulting fixed idea that design and tender documents have to be produced without errors. The introduction of the standard ÖNORM B 2203-1 and the ÖGG guideline for geotechnical design of underground works 10 years ago have provided the tools for designers to exploit the advantages of the NATM with the required comprehensibility and with more adaptability.