Research and application of a comprehensive forecasting system for tunnels in water-bearing fault fracture zones: a case study

In the process of tunnel construction, there is a high probability of encountering fault fracture zones. Tunnel deformation, water-inrush, and mud-inrush accidents easily occur in these sections. There is an urgent need for tunnel engineering to accurately predict the geological characteristics and spatial locations of water-bearing faults in front of tunnels. Based on the analysis of the advantages and disadvantages of various prediction technologies, a comprehensive water-bearing fault forecasting system is proposed, and the application process of this system is introduced in-depth for the Bifeng Temple high-speed railway tunnel project. First, the geological and hydrological conditions of the Bifeng Temple high-speed tunnel are analysed, and the orientations of the fault fracture zone and dense joint zone in the tunnel site area are determined. Then, tunnel seismic prediction (TSP) is applied to detect the spatial relationship and geological characteristics between the water-bearing faults and tunnel. To improve the forecasting accuracy, ground penetrating radar (GPR) is applied synthetically when approaching the fault. According to the comprehensive physical forecast results, the target area is verified by fixed-point advancing holes. The forecast results are consistent. Finally, the curtain-grouting method and three-step temporary inverted arch method are used to control the water-rich fault zone, and water inrush is successfully prevented. The monitoring and measurement results of the rock surrounding the tunnel in the fault zone verify the reliability of the control measures. This comprehensive forecasting system has been successfully put into practise in the water-bearing fault tunnel in Fujian, and it can play a guiding role in similar projects.