TBM DiGs is an international conference series that provides a specialized technological forum for discussing and exchanging knowledge related to TBM works in difficult ground conditions. This series covers a wide range of topics, including characterization of difficult ground, field observations and case studies, physical and laboratory tests, numerical modelling and techniques, treatments of difficult ground, TBM design and installation, tunnel support design, monitoring and risk management. TBM DiGs 2021 is the fifth conference in this series.

TBM DiGs 2021 is jointly organized by Montanuniversität Leoben and OEGG (Austrian Society for Geomechanics). The conference organizers would like to welcome researchers and practitioners involved with TBM tunnelling to TBM DiGs 2021 to share, to cooperate, and to progress.

The conference aims to bring together all who are interested in the use of tunnel boring machines in difficult ground, to review developments in the field over the previous two years, and to attempt to extrapolate for the near-term future. We anticipate that the conference will explore a great variety of topics.

Presentations in the following areas are invited:

• Rock – Very Hard and Abrasive rocks
• Rock – Squeezing ground
• Rock – Long and deep tunnels
• Soil – Sticky soil and Clogging
• Soil – Abrasive sand and wear problems
• Soil – High water pressure – hyperbaric challenges
• Mixed Ground conditions
• Innovation – New Technology (construction chemicals, sensory systems, big data, operational simulation)
• High Groundwater inflow / Gassy tunnels
• Extreme TBM tunneling (very small/big TBMs, remote areas, outer space construction)
• Manufacturing challenges and new developments
• Logistics and Site Management for challenging TBM tunneling