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The demand for efficient tunnels for traffic and utilities is increasing as living space above ground becomes scarce. This requires mechanized tunnelling technology, which sets standards regarding safety, profitability and environmental protection -in traffic tunnelling and in the trenchless construction of utility tunnels such as sewer, water supply, and cable tunnels, or oil and gas pipelines. Different types of machines and working principles have been developed to master the geological and hydrological requirements of tunnelling projects worldwide. Continuous research and development activities have lead to a constant improvement of tunnelling performance; today's TBM technology is therefore capable of handling unstable face conditions with water pressures up to 15 bar. This paper gives an overview of the development steps and of state-of-the-art tunnelling equipment for soft ground application, examines the feasibility of tunnel visions and highlights the innovative and current design approaches for today's specific project requirements. IntroductionThe increasing demand of mankind for higher comfort, safety and security standards is directly linked with the demand for better quality of life and greater mobility. The challenge for the construction sector is to meet this demand with rapid action to renovate and upgrade existing structures and construct new utility supply and transport systems. To be prepared for the future mission of constructing adequate and expandable high-efficiency infrastructure systems, rapid implementation is a prerequisite. Shield tunnelling technology has captured the attention of the public sector during the last two decades. It is a beneficial alternative to conventional tunnelling methods with its safe, settlement-controlled tunnelling process.Tunnel boring machines (TBMs) operate in geologies of all kinds, including hard rock, soft ground and mixedface conditions with high overburden and high hydrostatic pressures. The use of soft ground machines such as earth pressure balance shields (EPB) or slurry shields has allowed a considerable expansion of the scope of application of shield tunnelling, leading to increased economical Der Bedarf an leistungsfähigen Verkehrs-und Versorgungstunneln steigt mit der Verknappung des Lebensraums an der Erdoberfläche. Dies erfordert eine mechanisierte Tunnelbautechnologie, die Maßstäbe hinsichtlich Sicherheit, Wirtschaftlichkeit und Umweltschutz setzt -sowohl im untertägigen Verkehrswegebau als auch im grabenlosen Bau von Versorgungstunneln wie Abwasserkanälen, Wasser-und Leitungstunnel oder Öl-und Gasleitungen. Um die geologischen und hydrologischen Herausforderungen von Tunnelbauprojekten auf der ganzen Welt zu bewälti-gen, wurden unterschiedliche Maschinentypen mir verschiedenen Arbeitsmodi entwickelt. Permanente Forschung und Entwicklung führten zu einer steten Verbesserung der Vortriebsleistung; die heutige TBM-Technologie kann demzufolge auch Situationen mit instabiler Ortsbrust und Wasserdrücken bis zu 15 bar erfolgreich meistern. Der vorli...

A large number of successfully completed tunnelling projects in sensitive environments and airport areas show the highest technical and quality standards of mechanized tunnelling technology, mastering project challenges and individual tasks in the interest of customers, clients and the environment. The Forrestfield Airport Link, currently under construction in Perth, Australia, is one of these projects tackling challenges in an airport area sensitive to any kind of settlement and subsurface conditions. The paper highlights the project challenges that require a well‐adapted TBM concept and experience with the use of variable density TBM technology from the manufacturer's point of view.