Study on Soft Subgrade Settlement Via Optical-fiber Bidirectional Zigzag Based on Dofsm
Chaoqun WEI+, Qinglu DENG#, Kangqing DENG, Mengyao YAN, Weiwei SU
China University of Geosciences, China

Soft subgrade settlement has always been a prime factor affecting construction quality in coastal areas of China and other countries. Corresponding settlement and deformation monitoring are very essential, as they can carry out process monitoring for soft subgrade and nearby engineering. Conventional point-type monitoring instruments have the advantages of simple operation, reliable precision, and convenient data processing. However, the point-type sensors are only selectively installed in some locations, resulting in missing inspections, to a certain extent. Recently, distributed optical fiber sensing monitoring (DOFSM) technology has been studied deeply and applied consistently. Its full distribution, anti-electromagnetic interference, corrosion resistance, high precision, and other characteristics can accurately realize laboratory studies and engineering applications. This study designs a novel fiber layout mode with a bidirectional zigzag shape based on DOFSM to monitor the settlement and analyze the results. This work theoretically analyzes the feasibility of settlement and deformation monitoring of soft subgrade using optical fibers laid in a bidirectional zigzag. Then, the optical fibers data are analyzed via the designed bidirectional zigzag layout in the field monitoring study, and traditional point-type monitoring results are compared. The results show that the novel fiber layout in a bidirectional zigzag can theoretically carry out the conversion calculation from strain value to settlement value in monitoring soft subgrade. The settlement values of the monitored area can be obtained through the related calculation in the field monitoring using a theoretical formula. Compared to traditional monitoring results, DOFSM results using a bidirectional zigzag layout can obtain more on-site data, and the results are more accurate and more in line with the actual situation. Moreover, the three-dimensional camber graphics of soft subgrade with optical fibers data are obtained to analyze the changing trends. The results reflect the settlement and deformation trend of soft subgrade during the monitoring period more intuitively. DOFSM, in the form of the bidirectional zigzag layout, can better implement the settlement and deformation monitoring of the subgrade, providing a reference for further study.