Geological and hydrogeological risk assessment for tunnel excavation in water-bearing tuff zones: a case study

When a fault fracture zone composed of tuff occurs within a tunnel construction site, the surrounding rock mass becomes highly unstable, significantly increasing the risk of geological hazards. To detect the location of such fracture zones ahead of tunnel excavation and to take timely preventive measures, this study develops a comprehensive geological forecasting system. Based on the No. 5 Tunnel of the Yinchuo-Jiliao Project, a comprehensive geological forecasting system combining geological analysis, seismic wave method, and polarization excitation method was utilized to conduct advanced prediction of the location of the fractured zone and groundwater development ahead of the tunnel face. Additionally, a treatment plan for the fractured zone in the unexcavated sections was formulated based on the results of the advanced geological forecasting. This approach effectively prevented geological hazards during construction, ensuring the safe and efficient operation of the Tunnel Boring Machine (TBM) within the tuff fault zone. The research results provide practical guidance for the prevention and mitigation of geological disasters in similar geological settings.