What is it about?

The overall goal of this study intends to adopt a technical route combining numerical simulation, disease detection and on-site vibration monitoring. Firstly, based on visual inspections, axial cracks and voiding were observed in the CA mortar layer of a section in Shanghai-Hangzhou railway line. The defect characteristics are then reproduced through finite element analysis in order to establish the relationship between the average velocity and CA mortar defect distribution. Secondly impact imaging method and distributed optical fiber sensing are applied in field test to determine the corresponding relationship between the track slab structural quality and vibration signal. Hence, by combining these results the fault detection is completed.

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Why is it important?

This work yielded the following findings: (1)Different propagation characteristics of elastic wave can be used to diagnose structures defective areas, such as energy, wave shape, amplitude and spectrum. (2)-OTDR depends mainly on the monitoring of the Rayleigh backscattering to determine the transmission loss in the fiber under test. The sensing measurands include fully distributed vibration signals. (3)The numerical simulation results show that the defects in the CA mortar layer increases the vibration response with an amplification factor more than 2. A 10% faulty CA mortar causes excessive resonance of the track slab. (4)Based on visual inspection, The DOFS monitoring and impact imaging method results shows good agreement about the influence of structural defects on the track slab response with and response magnification above 2. (5)Furthermore, these techniques have high precision and they are technically feasible with a large-scale measurement, regardless of external electromagnetic perturbations.

Perspectives

This manuscript provides a feasible and effective vibration monitoring method and idea for railway researchers to inspect long-term degradation and potential risks to the operation safety of high-speed train. This method can be also extended to fault detection in pavement road and loading conditions and other civil vibration-based sensing projects.

Baye Mbaye Diouf
Shanghai Jiao Tong University

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This page is a summary of: Study of a Space-Time Monitoring of High-Speed Railway Underline Structure Using Distributed Optical Vibration Sensing Technology, Shock and Vibration, April 2019, Hindawi Publishing Corporation, DOI: 10.1155/2019/9263259.
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