Application of Direct Current Method and Seismic Wave Method in Advanced Detection of TBM Construction Tunnels

Over the past decade, the application of Tunnel Boring Machines (TBMs) in tunnel construction has increased significantly. During the construction process, numerous unfavorable geological structures, especially water-conducting structures, are encountered. The commonly used Tunnel Seismic Prediction (TSP) method often cannot accurately interpret water-conducting features, while resistivity methods are sensitive to low-resistivity bodies, which are frequently associated with water channels. Due to the limited space and the surrounding pipe lining near the tunnel face, as well as the difficulty in drilling boreholes under TBM construction conditions, this paper proposes a novel electrode arrangement method that replaces rigid electrodes with flexible electrodes installed on the sidewalls. This approach overcomes the difficulty of deploying traditional electrodes downward in TBM tunnels. A simple direct current resistivity configuration was employed for field testing during the construction of the Guiyang Metro Line 3 TBM tunnel, and the results were compared with those from the Tunnel Seismic Prediction (TSP) method. The experimental results demonstrate that the improved DC resistivity method achieves high detection accuracy for water-conducting structures within a range of 30 m, showing strong consistency with the TSP detection results. This validates the feasibility and accuracy of the method, effectively addressing the challenges associated with traditional electrode deployment in TBM tunnels while compensating for the limited response of seismic methods to water-bearing structures. However, the effectiveness near the tunnel face remains suboptimal, with insufficient current distribution—an area requiring improvement, potentially by increasing forward current supply or further optimizing the electrode layout. Additionally, the study highlights the limitations of relying solely on a single advanced prospecting method. It suggests adopting an integrated approach, primarily based on seismic methods supplemented by electrical methods, to enable joint detection and interpretation, thereby minimizing the risk of accidents during construction.