ABSTRACT
During construction of the cased tunnel groundwater gushed out with a maximum discharge exceeding 27 ton/min, endangering the stability of the excavated face and seriously hindered the construction progress of the tunnel. The groundwater inflow with a discharge of exceeding 20 ton/min lasted more than 30 days. Emergency drainage and reinforcement measures were immediately applied to avoid groundwater inrush-induced catastrophic collapse from the excavating face. Supplementary geological exploration was carried out before long to investigate possible causes. After the geological conceptual model has been figured out and possible influencing factors that account for the water inrush event has been understood, groundwater drainage and grouting improvement measures were used to overcome the groundwater inrush event. This manuscript introduces the background of the tunnel project and the process of water inrush, summarizes the results of supplementary geological exploration, and finally puts forward suggestions on the construction of tunnels in the argillite-like formation.
