Experimental Study on Slope Deformation Monitoring Based on a Combined Optical Fiber Transducer

Abstract

Landslide monitoring is very important in predicting the behavior of landslides, thereby ensuring environment, life, and property safety. On the basis of our previous studies, a novel combined optic fiber transducer (COFT) for landslides monitoring and the related analysis methods are presented. Based on the principles of optical fiber microbending loss, the empirical formula of the shearing displacement of sliding body versus optical loss was established through a stretching test of optical fiber bowknot. Then the COFT grouting direct shearing tests, a large-scale landslide model test, and numerical modeling verification with FLAC3D are carried out. According to the results, the initial measurement precision of the designed COFT in sandy clay is 1 mm; its monitoring sliding distance is larger than 26.5 mm. The calculated values based on empirical formula are in good agreement with the laboratory tests and numerical simulation results. When the ratio of cement and sand in mortar is 1 : 5, the error between the calculated displacement and the measured displacement of sliding surface is the smallest. The COFT with expandable polystyrene (EPS) as its base material performs better in monitoring sandy clay slopes because both the error and the mean square deviation of the empirical formula are smaller.

Recent Phenomenal and Investigational Subsurface Landslide Monitoring Techniques: A Mixed Review

“…To increase the measuring range, Zhu et al [47] created the second generation "combined optic fibre transducer" (COFT), with the base material being expansile polyester ethylene (EPS). Zheng et al [84] used physical large-scale modeling to build an empirical formula for an innovative (COFT) that used OTDR based on the concepts of optical fiber micro bending loss. The COFT has a maximum sliding distance of 26.5 mm and an accuracy of 1 mm.…”

“…Different lengths of capillary steel pipes were arranged to determine the sliding surface location with a spatial resolution of 250 mm. Zheng et al [84] employed laboratory shear testing and field experiments in which many fiber-optic displacement sensors (FODSs) were linked in series. The starting measurement of the QDFODS was 0.98 mm, and the maximum displacement was 36 mm.…”

“…The most effective material and the best cement-to-sand ratio in mortar were expandable polystyrene (EPS) and 1:5, respectively. The following are the capabilities of COFT fibers: (1) accurately predict the slide direction; (2) low cost; (3) remote, long-term, and real-time monitoring; (4) data collection takes seconds; and (5) distributed across numerous kilometers with great strain accuracy [47,58,84,85].…”

Design and Simulation of Fiber Optic Cable using SolidWorks for Landslide Monitoring

“…Despite fiber optic is not new for landslide monitoring, the development and integration of new concepts in it would compete favorably with the existing monitoring concept and expand the possibilities and perspectives. Since fiber optic is relatively small, it has better reliability, faster transmission, higher flexibility, longer sensing distance, and immune to electromagnetic interference, it is the best choice for landslide monitoring in the future [17][18][19][20][21][22][23]. There are many types of fiber optic cable such as drop cable, indoor cable, outdoor cable, and armored cable [23].…”