Multi-source seismic geological ahead-prospecting for TBM tunneling in fractured strata: improved strategies and case studies in a water conveyance project, China

The Tunnel Boring Machine has inherent limitations in adapting to adverse geological conditions. When operating in complex strata, encounters with challenging geological formations such as faults and fractured zones can result in tunnel collapses or TBM blockages. This article outlines the successful implementation of a multi-source seismic prospecting strategy designed to achieve advanced prediction of unfavorable geological bodies in a water conveyance project in Northwest China. Due to long-distance broken strata along the construction path, to ensure safety, a single shield TDM replaced the initial open type TBM for the starting section of TBM3-2. With the change in the tunnel environment prompted by the TBM modification, the conventional active source seismic prospecting method previously employed in the open type TBM section became unsuitable. Consequently, we adopted TBM drilling source seismic prospecting technology, refining the arrangement of geophones to capture high-quality seismic signals. Employing this strategy allowed for continuous seismic ahead prospecting across the entire tunnel, providing crucial data to guide safe TBM operation and tunnel support. The multi-source seismic exploration strategy has notably enhanced the TBM's capability to manage complex geological scenarios, such as long-distance fractured zones. This approach has been instrumental in bolstering risk warnings and minimizing TBM blockages, effectively addressing and resolving engineering challenges.