The development of the NATM - a historical review / Die Entwicklung der NÖT - ein geschichtlicher Rückblick

The NATM is essentially a way of thinking rather than a construction method; we could also say a school of tunnelling. Understanding of the NATM depends on the era, local preferences and traditions and also on the particular interpretation by the responsible person. Accordingly, national versions of the NATM or similar tunnelling methods have been developed all over the world. The main theme of the NATM is the use of the load-bearing capacity of the rock mass and the control of support measures based on the interpretation of observations and measurements. This adaptability of the tunnelling method to the conditions observed is typical for the NATM and requires a correspondingly adaptable construction contract with clear assignment of risk. The development of the NATM has been decisively influenced by the improvements in shotcrete technology and the use of new support measures like rock bolts, pipe umbrellas and yielding elements. Three-dimensional measurement of the deformation of the cavity today enables comprehensible control of NATM drives. The introduction of the ÖGG guideline for the geotechnical design of underground structures by cyclical construction in 2001 provided a regulation for the comprehensible engineering design and construction of underground structures. The conditions of contract for underground construction B2203-1978 already contained provisions for the agreement of "rock quality classes" between the client and the contractor. The B2203-1994 introduced the model of a tunnelling matrix. This provides an unambiguous and transparent basis for estimation and invoicing.