Geological investigation and treatment measures against water inrush hazard in karst tunnels: A case study in Guiyang, southwest China

• Water and mud inrush accident in tunnel is introduced, and the causes are analyzed. • An innovative scenario for the treatment of water and mud inrush in tunnels is proposed. • Innovative scenario has low cost and environment-friendly characteristic. • The design, construction, mechanism and advantages of the scenario are introduced. • Monitoring results and tunnel operation show that the measures has achieved good results. Unfavourable geological disasters, such as water inrush and gushing mud, are often encountered during tunnel construction in karst areas. Whenever a large-scale water and mud inrush hazard occurs during excavation, it could cause great economic loss and, even, casualties. This paper presents a case study of water inrush hazard and treatment of large-section filled karst conduits during the construction of the running tunnel of Guiyang Rail Transit Line 1. Various causes of water and mud inrush are systematically analysed. Through the comparison and analysis of various solutions to treat the karst conduits, an innovative scenario for the treatment of water and mud inrush in tunnels constructed in karst areas is proposed. A discharge channel comprising drainage shafts and connecting passages is constructed, so that confined karst water can flow towards the ground surface by itself. Compared with common treatment methods, this has many features, including: not changing the original groundwater system, a short construction period, low cost and environment-friendly characteristics. Therefore, this case history can be used as a reference for the treatment of water and mud inrush in similar situations.