Application Of Distributed Optical Fiber Sensor In The Gravity Dam Monitoring

The crack of concrete gravity dam is a dangerous factor for the dam body safety, so cracks is the importance in concrete gravity dam safety monitoring. The conventional monitoring system is limited by and can not monitor the dam body continuously for the time and space, therefore a new kind of detecting techniques-distributed optical fiber sensor is found to solve these problems well. The time of development and application for distributed optical fiber sensor is no long, so they have many problems when used in projects and some of their theories are not integrated and in a search phase. At the same time, gravity dam is very huge and we can not set sensors in the whole dam, so how to select the appropriate set for optical fiber sensor is an important problem which needs to be solved. Otherwise, because of the monitoring mechanism in detecting cracks, we need to select an appropriate network style when using the distributed optical fiber sensor.To solve two problems which are referred above, this article calculates through the finite element method, analyze the differences in dam body stress and compare the characteristics of all dams body stress, then it gives a universal conclusion and selects an appropriate extent for setting sensors. At the same time, it contrasts several different network styles and chooses the most appropriate one for the selected extent. It mainly concludes:(1) It reviews the history of dam safety monitoring and summarizes the flaw and insufficiency in the traditional safety monitoring, then it advances the feasibility when using optical fiber sensor in dam monitoring.(2) Learning about the tectonic feature of fiber and principles of each kind of optical fiber sensor, selecting two kinds of optical fiber sensors for detecting the concrete crack(3) Studying the principles, monitoring mechanism and usage process of two kinds of crack detecting sensors, finally choosing an appropriate one for crack monitoring in gravity dams.(4) It selects some gravity dam models for calculation and selects the dangerous extent where sensors will be set by analyzing the dam body stress. This extent is 0.15 height of the dam from the dam heel to the dam crest on the upstream surface and 0.1 height of the dam from the dam site to the dam crest on the downstream surface.(5) After analyzing several kinds of different network styles, it chooses an appropriate one according to the comparison and gives some practical applications in projects.