Monitoring of lateral displacements of a slope using a series of special fibre Bragg grating-based in-place inclinometers

Abstract

Traditional in-place inclinometers are widely used for monitoring displacements inside a slope. However, these traditional inclinometers have several disadvantages such as electromagnetic interference, signal loss for long distance transmission, gravity dependence and poor durability. Scholars have proposed fibre Bragg grating (FBG)-based in-place inclinometers which can overcome these limitations. However, all such in-place inclinometers are based on the relative displacement between two tips of the rigid segment, but the deformation of the segment is not considered in the calculation, which is not consistent with the actual condition. The error of measurement is due to linear superposition. According to classical indeterminate beam theory, the authors developed a new type of FBG-based in-place inclinometers where the deformation of the segment is coordinated with the casings installed in boreholes. This type of FBG-based in-place inclinometer has been fabricated and calibrated in the laboratory. The measured displacement data are in good agreement with theoretical results obtained using equations derived by the authors based on classical beam theory. After the laboratory calibration, a series of FBG-based in-place inclinometers have been installed in one vertical borehole in a slope in China. Monitoring data of all FBG wavelengths have been collected in rainy and dry seasons, and have been analysed in this paper. It has been found that the slope moves quickly in the rainy season and remains stable in the dry season.

Study on the Deformation Measurement of the Cast-In-Place Large-Diameter Pile Using Fiber Bragg Grating Sensors

“…Compared to the conventional monitoring technologies, FBG technology is formed by using the phase mask method to change the refractive index of the optical fiber [12,13,14,15]. The FBG sensors can measure the distribution of strain, temperature, displacements, and so on with high accuracy and stability [16,17,18,19,20,21,22,23]. This technology has been successfully applied to monitor the field performance of reinforced slopes, dikes, and bridges.…”

Internal Deformation Monitoring of Slope Based on BOTDR

“…Recently some researchers have begun to advocate this technology into the slope monitoring. Pei et al [13], Ma and Yao [14], Zhang et al [15], and Wang et al [16] proposed FBG based in-place inclinometer and Zeni et al [17] developed BOTDA based in-place inclinometer, which overcomes the disadvantages of conventional inclinometer including electromagnetic interference, gravity dependence, poor durability and stability, and signal loss for long distance transmission. However, FBG is a quasi-distributed technology which may affect the position accuracy of the sliding surface.…”

Introduction to an FBG-based inclinometer and its application to landslide monitoring

“…Recently, the fiber optic sensing technologies have been advocated for slope monitoring by some scholars [1][2][3][4][5][6][7][8]. Different types of FBG-based in-place inclinometers have been developed, which demonstrated various features, such as small size, superior chemical resistance and stability, immune to electro-magnetic interference, and quasi-distributed monitoring capability [9][10][11][12][13]. This technology is especially suitable for automatic and long-distance monitoring in landslides.…”