TBM tunnelling under adverse geological conditions: An overview

•Classifications of adverse geological conditions for TBM tunnelling are proposed.•The mitigation measurements for TBM tunnelling under these conditions are discussed.•The further researches conducted for coping with these problems are emphasized.

The adverse geological conditions frequently encountered during TBM tunnelling present great challenges, and may trigger potential hazards if no precaution and treatment measures are taken. Comprehensive studies on adverse conditions are essential and critical to successful TBM tunnelling. In this overview paper, attempts are made to define the adverse geological conditions for TBM tunnelling. A simple classification and the influencing factors related to the adverse geological conditions are presented for better understanding of the topic. The main problems involved and the corresponding mitigation measures for TBM tunnelling under adverse geological conditions are discussed. Finally, further research needs for better coping with these problems are emphasized.