Application of Optical-Fiber Bragg Grating Sensors in Monitoring the Rail Track Deformations

Abstract

The lateral flow of ballast during the passage of trains can reduce the stability of rail tracks. Therefore, it is important to monitor and restrain the movement of ballast accordingly in order to prevent track misalignment. This current study explored the use of optical-Fiber Bragg Grating (FBG) sensors to measure the lateral displacement of unreinforced and geogrid-reinforced ballast. The tests were conducted on fresh latite basalt at a loading frequency of 20 Hz and up to 250 000 load cycles. The test results showed that the FBG sensing system is fully capable of measuring the lateral displacement of ballast under high-frequency cyclic loading. A comparison of strains obtained from FBGs installed at different depths along the ballast depth is made and the lateral strain profiles are measured. Moreover, an empirical model to convert the FBG strains to an equivalent lateral displacement of ballast is proposed to effectively use this technology in realtime monitoring of track deformations. Moreover, an empirical model to convert the FBG strains to an equivalent lateral displacement of ballast is proposed to effectively use this technology in real-time monitoring of track deformations.

A laboratory investigation to assess the functioning of railway ballast with and without geogrids

“…A similar observation with regards to strains in FBG sensors for the ballast reinforced with geogrid G3 was made by Hussaini et al (2015b). A closer look at Figure 3 depicts that both the FBG strains and the lateral displacements from LVDTs, in a macroscopic sense, follow a similar strain evolution pattern with load cycles (N).…”

“…The Bragg wavelength is a function of the refractive index of the fiber core and the grating period, and this condition is represented by Equation 1. The operating principle of fiber Bragg grating (FBG) sensors involves monitoring of the wavelength shift in the reflected wavelength spectrum, and then converting it to strain in FBG sensor by using the relevant calibration charts (Hussaini et al 2015b). …”

Using FBGS to estimate the horizontal response of a monopile in a geotechnical centrifuge

“…For such reason, it has been increasingly used. In geotechnical laboratory and field testing, FBGS have been used to measure the load transfer of the model pile (e.g., Lee et al, 2004), the strain distribution along the soil nails during pull-out test (e.g., Zhu et al, 2007Zhu et al, , 2011Hong et al, 2017) and the transversal displacement of ballast under cyclic loading conditions (e.g., Hussaini et al, 2015). Besides, FBGS have been used to monitor the dynamic process of the wind turbine blades (e.g., Park et al, 2011), large pile under vertical driving conditions (e.g., Doherty et al, 2015) and strains of buried pipelines under different external loads (e.g.…”

Influence of Particle Gradation and Shape on the Performance of Stone Columns in Soft Clay

“…The conversion factors were determined by comparing the 2D porosity values obtained for cross-sections that did not undergo any change in the porosity and the initial porosity obtained via weight- In test T4, a number of optical Fibre Bragg Grating (FBG) sensors and miniature pores pressure transducers were installed to measure the lateral strain of the column and induced pore pressure in the clay located adjacent to the column, respectively. The details of strain measurement using FBG are presented in Hussaini et al (2015). The FBG sensors were glued on a flexible and grooved rubber strip placed along the length of stone column at an offset of approximately 10 mm from the column edge.…”