This study employed distributed fiber-optic sensors (DFOSs) to examine twin-tunnelling-induced pile bending responses and to identify the primary influencing factors across different tunnelling stages. The high spatial resolution of DFOS measurements enabled detailed analysis of the bending strain energy (U) along the pile. Throughout each tunnel advancement, both U and negative peak bending moment (NPBM) underwent one loading and one unloading process, exhibiting a consistent positive correlation. This investigation introduced two crucial parameters: the negative peak energy density (Un), derived from NPBM, and the mean strain energy density (Um), derived from U. The long-term measurements revealed that the Um/Un ratio remained within a narrow interval (width < 0.10) throughout most Lpt intervals, allowing a zero-intercept linear function to serve as the development line for normal strain energy concentration. The level of strain energy concentration, which is correlated with risk, are quantifiable via the deviation value of Un from the development line. In particular, positive and negative deviation values of Un occurred at the peak and steady states, respectively, corresponding to high and low strain energy concentrations. Additionally, the development of pile-soil interface contact stress was investigated using threedimensional numerical modelling, providing deeper insight into the loading and unloading mechanisms.
Key Words
distributed fiber-optic sensors; loading and unloading processes; pile bending responses; strain energy concentration; twin tunnels
Address
Liangyi Cai, Tingjin Liu, Huashan Zhong, Junxian Xiao, Zhijie Peng, Zhan Liang — School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, Guangdong, China
Zhixiong Li — Guangzhou Metro Construction Management Co., Ltd, Guangzhou 510220, Guangdong, China
Wufeng Mao — Guangzhou Metro Design and Research Institute Co., Ltd., Guangzhou 510010, Guangdong, China
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