Theoretical and experimental study on the fiber Bragg grating-based inclinometer for slope displacement monitoring

Landslide monitoring and forecasting have always been important research topics in geotechnical engineering. This study presents a self-designed inclinometer using fiber Bragg grating (FBG) sensing technology, which was used to obtain the slope internal displacement. It is well known that FBG sensors can be effectively utilized for strain measurement; however, it is difficult to directly use FBG strain sensors to measure the displacement. Therefore, based on the conjugate beam method, a mathematical equation to convert strains to lateral displacements is established, which has been verified by the finite element numerical model considering different beam lengths and two bending types. Furthermore, field monitoring suitability tests of an FBG-based inclinometer were carried out, which shows that the proposed deflection solution based on FBG strain sensors can accurately calculate the shear displacement of a slope.