Natm - Design Steps And Contractual Matters

The construction of tunnels and the development of tunnelling methods in a country are strongly influenced by the Geographical situation, topography, existing infrastructure and buildings, environment, natural resources, geology, hydrology, the demand for underground works, Political, social, economical situation, Legal status and competence of owners, the availability of qualified workforce, mining traditions and contractual attitude. The protection of the population against emissions as well as the protection of the environment and natural resources require an increasing number of large underground constructions. In terms of tunnelling, the geology in Austria is generally difficult and tends to change rapidly along the tunnel route. Tunnelling in the Alps means facing a high overburden and, in places, heavily squeezing rock. Further more tunnelling in urban environments is gaining importance. After the mid-fifties of the last century new materials, namely shotcrete and rock anchors, replaced the old timber support and the masonry lining was abandoned for a permanent lining of in-situ concrete. In addition, the waterproofing quality of tunnels was considerably improved with the standardized use of synthetically membranes and fabrics. At this time Austria had a number of brilliant engineers like Rabcevicz, Muller, Patcher, Loafer, Seeder, ital. who greatly influenced and promoted the development of tunnelling in Austria by innovative ideas. Most important was the development of ATM (New Austrian Tunnelling Method), which introduced the observational approach in tunnelling. Owners experienced in tunnel design and construction together with specialised contractors developed an On-site decision making procedure, which became common practice in Austrian tunnelling. The technological development and the engineering practice in tunnelling paved the way for new theoretical explanations to substantiate an economically beneficial design approach. The Austrian way of tunnelling foresees immediate and joint decisions by both partners within the contractual frame work. This ensures an immediate and effective response to changes in ground conditions. The ATM needs qualified and experienced owners, designers and contractors, qualified and authorised engineers on site, as well as a qualified and experienced workforce and a suitable contractual model. An important feature of the Austrian tunnelling community is to ensure a good cooperation between all parties to a contract. Technical questions regarding safe, fast and economical tunnelling take priority over contractual considerations. This approach is of general benefit to all parties. It is based on a profound technical expertise and a genuine willingness to compromise. As a rule tunnelling works in Austria are executed on the basis of unit price contracts. The Austrian way of tunnelling foresees immediate and joint decisions by both partners within the contractual frame work. This ensures an immediate and effective response to changes in ground conditions. The ATM needs qualified and experienced owners, designers and contractors, qualified and authorised engineers on site, as well as a qualified and experienced workforce and a suitable contractual model. An important feature of the Austrian tunnelling community is to ensure a good cooperation between all parties to a contract. Technical questions regarding safe, fast and economical tunnelling take priority over contractual considerations.