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Description
Urban shield tunneling faces severe challenges from deep-seated hidden geological hazards. Constrained by limited penetration depth and complex urban electromagnetic interference, traditional geophysical methods struggle to achieve dynamic monitoring of deep hazards during excavation. This paper proposes a 3D dynamic absorbtion -based muography technology tailored for shield tunneling environments. To overcome the effects of continuous dynamic displacement and complex urban background interference, a data fusion strategy based on a "quasi-static approximation" and a refined "strata-surface building" quantitative correction model were developed. Furthermore, a highly integrated, automated detection hardware and software system was engineered to withstand the extreme conditions inside the tunnel boring machine (TBM).
A long-term field dynamic experiment was conducted on Shenzhen Metro Line 25, achieving continuous monitoring over 492 TBM rings (736.8 m in total). Field results demonstrate that: (1) The system achieved real-time dynamic perception of the strata ahead of and above the TBM. It successfully detected and 3D-reconstructed a utility intersection cavity (approx. 27.6 m³) located 3.5 m above the tunnel, with spatial positioning highly consistent with ground-truth verification via field manhole inspection. (2) By correlating with known utility distributions, the engineering applicability boundaries of the system at typical depths were delineated, verifying its meter-level spatial resolution. (3) Hypothesis testing based on empirical data resampling confirmed the system's ultimate detection sensitivity for micro-cavities as small as 1 m³ within the strata. This study not only validates the engineering feasibility of dynamic muon imaging in urban shield tunneling but also clarifies its applicability boundaries and resolution characteristics, providing reliable technical support for quantitative risk management in complex underground engineering.