ABSTRACT
The utilization of shield machines for cutting through underground reinforced concrete (RC) structures has become a common solution in construction practice. However, the precise locations of the RC wall and rebar inside are challenging to be ascertained by conventional geological prospecting methods, which may result in difficulties in shield driving control. To address the issue, this paper proposed an inversion method based on the shield driving parameters and vibration signals. The results showed that based on the changing pattern of the driving parameters, the exact timing of the wall-cutting process can be determined by inversion analysis. The characteristic stages in the wall-cutting process can be identified according to the evolving pattern of the time-domain indices of vibration signals. Moreover, the precise timing of the rebar-cutting process can be discerned by analyzing the periodic characteristics of the vibration signals. The results of inversion analysis indicated that the cutting process of the front row of main rebar lasted for approximately 23 minutes, with the shield machine advancing approximately 55 mm and rotating for 15 cycles, and the cutting process of the rear row of main rebar lasted for approximately 15 minutes, with the shield machine advancing approximately 42 mm and rotating for 12 cycles. This suggested that the rebar-cutting process was safe and smooth. The Metro Jet System reinforcement behind the wall facilitated the effective severing of the rear row of main rebar. The methodology can be applied to analogous projects for identifying the real-time cutting status of the shield machine. The findings presented in this paper can lead to a deeper comprehension of the concealed construction process that the shield machine cuts through the RC diaphragm wall.
