| Due to limited sites and space, flood discharging of high dams only through dam is difficult to meet the design requirements, so it always uses special flood-releasing facilities for unusual flood release. the Longtaitou & Longluowei Spillway Tunnel are used widely in actual engineering, for example, Ertan, Xiluodu, and JinpingⅠHydropower Station. Because of High Head, the velocity of flood discharging tunnel at downstream can be 40m/s～50m/s. In the circumstances, cavitation erosion is very easy to take place. Therefore, it is a protuberant problem for the safety of flood discharging Tunnel.How to make sure the safety of flood discharging, and how to in time identify & early warn the cavitation erosion when appears is a stringent problem.Because flood discharging tunnel ,which belongs to underground engineering, has huge structure, at present, tunnel cavitation erosion when discharging flood is mainly depend on artificial method and point sensor to check. Artificial method ,which not only obviously slow responses, and also is time consuming and ask for much manpower, can be only carried out after flood discharging, and can not find out and monitor the process of cavitation erosion. At the same time, point sensor, the coverage of which is limited, is inclined to become invalid because of corrosion.With the development of optical fiber Sensing Technology, it becomes possible that real-timely monitoring flood discharging tunnel cavitation erosion. In this thesis, the thought that detecting flood discharging tunnel cavitation erosion using distributed optical fiber is first put forward, and also the theory is described. This thesis analyzes the vibration characteristic of distributed optical fiber Sensor, comparing to vibration displacement sensor and acceleration sensor which are used widely in engineering. Moreover, the identification of simulative flood discharging tunnel concrete lining cavitation erosion is studied using distributed optical fiber vibration test system. |
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