Surface-wave geological exploration method based on Tunnel Boring Machine (TBM) drilling noise

Tunnel Boring Machines (TBMs) have become an effective equipment to construct tunnels in urban underground spaces. TBM has a low ability to cope with unfavorable geological situations such as faults, boulders, and uneven bedrock. These can cause geo-hazards like TBM jamming, cave-ins, and water gushing, which often lead to deaths and economic losses. Therefore, accurate, and real-time geological prospecting is necessary for tunnel face stability and ensuring tunnel construction safety. To address this, a surface-wave geological prospecting method based on TBM drilling noise has been proposed in this study. The characteristics of the TBM drilling noise and formation of surface waves in the ground were studied, which provides a basis for designing a new observation system for utilizing the vibrations or drilling noise caused by the TBMs. A complete workflow, which includes the extraction of surface waves from the TBM drilling noise, was then developed based on seismic interferometry, f-k filtering, and dispersion measurement, and joint velocity inversions based on the fundamental-mode and highermode dispersion curves. Compared with traditional methods, this method can obtain more accurate velocity distribution of underground media. As a result, a real-time detection and timely estimation of adverse geologic conditions at the front of the tunnel face during TBM drilling was achieved. Consequently, the feasibility and applicability of this method were then verified by field application in the Jinan Subway.