Processes and sources identification of intermittent karst water inrush in Xiakou Tunnel

Abstract

The investigation and prevention of karst water inrush is a difficult problem in tunnel construction. The Xiakou Tunnel has a long history of karst water inrush.To identify the source of intermittent water inrush and explore the controlling effect of karst water system to the process of water inrush, the hydrogeological survey, hydrological and hydrogeochemical methods were used to identify the sources and processes of water inrush. The results show that, there is a groundwater divide at the area of Mengjialing, and the groundwater in the northern and southern area discharge into Xianglongdong and Xiakoudong, respectively. In the events of concentrated water inrush, the total amount of event water inrush has a significant linear positive correlation with the rainfall event, and the hydrogeochemical composition of the water inrush is very similar to that of the four blind drainage ditches, which indicates that all these water inrushes and blind drainage ditches come from the karst water in the northern part of the tunnel. During the stable drainage period, the karst water in the northern part of the tunnel is mainly discharged through the blind drainage ditch on the north of the right tunnel, while the groundwater of other three blind drainage ditches come from the fissure water in clastic rock.The concentrated water inrush point is located on the surface of saturated zone in the karst water system of Xiakou. The heavy rainfall events made the upper part of tunnel to be filled with karst water.The water inrush was caused by intercepting the fast flow in karst channel, and small part of base flow was mixed into the water inrush. In the study of karst water inrush, the comprehensive utilization of multi-technical methods and multi-information verifications can improve the accuracy in the source identification of water inrush