New Austrian Tunneling method

New Austrian Tunneling method
Name	New Austrian Tunneling method
Inventor	Karl von Terzaghi; Friedrich Rinne; Rudolf Schubert
Year	1950s
Country	Austria
Type	tunneling method

New Austrian Tunneling method The New Austrian Tunneling method is a geotechnical engineering approach for underground excavation that emphasizes mobilization of surrounding rock mass strength, systematic support sequencing, and observational adjustments during construction. It integrates empirical experience from projects across Europe, the United States, and Japan with theoretical developments in rock mechanics and soil mechanics. The method influenced modern tunneling contracts, construction practices, and standards adopted by organizations such as British Standards Institution, International Tunneling and Underground Space Association, and national rail and highway authorities.

Introduction

The New Austrian Tunneling method (NATM) treats the tunnel and surrounding formation as an integrated structural system, relying on the rock mass to provide primary support while using shotcrete, steel ribs, and rock bolts as flexible reinforcements. Early proponents and technicians implemented the method on projects associated with the Austrian Federal Railways, Deutsche Bahn, and major hydroelectric schemes like Rheinfelden Power Station and other Alpine tunnels. Influential figures linked to the method include Karl von Terzaghi, Ludwig von Tetmajer, and later adopters in the engineering firms Ove Arup & Partners and Electricité de France.

History and Development

Origins trace to mid-20th-century advances in soil mechanics and rock mechanics led by academics and practitioners at institutions such as the Technical University of Vienna and Imperial College London. The method crystallized in the 1950s and 1960s through projects in the Austrian Alps, with formalization by engineers associated with firms like Voestalpine and consulting groups tied to the European Coal and Steel Community. Key milestones include adoption in major European infrastructure like the Gotthard Base Tunnel precursor studies, integration into standards by the International Organization for Standardization, and transnational diffusion via conferences of the International Society for Rock Mechanics and Society for Mining, Metallurgy & Exploration.

Principles and Methodology

NATM principles emphasize observational design, convergence-confinement concept, and staged support to allow controlled deformation that mobilizes rock arching. The method draws on theoretical foundations laid by Karl von Terzaghi, practical formulations by Rudolf Schubert, and analytical work from researchers at Massachusetts Institute of Technology and ETH Zurich. Core methodological elements include measurement-led adaptations using instrumentation developed by suppliers like Geokon and firms such as Fugro, with analysis methods comparable to those in publications from American Society of Civil Engineers and Institution of Civil Engineers.

Design and Analysis Considerations

Design under NATM requires assessment of geological conditions characterized using classification systems like the Rock Mass Rating and the Q-system devised by Norwegian Geotechnical Institute researchers. Engineers integrate laboratory data from institutions such as Lehigh University and École Polytechnique Fédérale de Lausanne with in situ tests performed by contractors like Balfour Beatty and Hochtief. Numerical analyses often employ finite-element and boundary-element software developed by companies such as Plaxis and ABAQUS and align with guidelines from Eurocode committees and national transport agencies including Transport for London.

Construction Techniques and Equipment

Practical implementation uses sequential excavation, shotcrete application, systematic rock bolting, and installation of lattice girders or steel ribs. Equipment commonly used derives from manufacturers like Atlas Copco, Sandvik AB, and Herrenknecht for drilling, spraying, and mechanized excavation. Support materials include fiber-reinforced shotcrete produced by suppliers linked to Sika AG and conveyor and mucking systems characteristic of projects undertaken by companies such as Skanska and Strabag.

Applications and Case Studies

NATM has been applied to rail tunnels, road tunnels, hydroelectric penstocks, and underground caverns in varied geology across projects like the Arlberg Tunnel, sections of the Mont Blanc Tunnel rehabilitation, and mountain tunnels in the Alps. International case studies include adaptations in the Japanese Alps for projects by Japan Railway Construction, Transport and Technology Agency and urban tunneling in cities served by New York City Transit Authority and Paris Métro expansions. Major infrastructure programs by entities like Swiss Federal Railways and Austrian Federal Railways contain documented NATM sections illustrating observational design outcomes.

Safety, Monitoring, and Quality Control

Safety protocols incorporate continuous monitoring of deformation, stress redistribution, and groundwater behavior using instruments from Geosense and Rocscience. Quality control follows contractual regimes influenced by procurement practices in European Union directives and national regulators such as Federal Highway Administration and Bundesanstalt für Straßenwesen. Emergency response planning interfaces with local authorities like Red Cross chapters and civil protection agencies during construction incidents.

Advantages, Limitations, and Criticisms

Advantages cited include economical use of indigenous rock strength, adaptability in variable geology, and reduced permanent support when compared to rigid linings used in projects by firms such as Bechtel. Criticisms involve dependence on experienced personnel, potential for larger-than-expected deformations in weak or water-bearing ground—issues studied by United States Geological Survey and academic groups at University of Cambridge—and challenges integrating NATM with large-diameter mechanized tunnel boring machine approaches favored by contractors like Herrenknecht AG.

Category:Tunnelling