| There are large number of dams in our country. The earth dam as the old dam type has become the leading dam type over the dam project because its simple construction, low cost and it can adapt to the complex geological conditions etc. However, roots rock lost and collapse would occur to the earth dam when the floods came and eroded because of poor foundation. If the danger was found later and led to the rescue materials that needed inputs are not timely, it will cause the earth dam body exposed soil, and soil away quickly with water flow, then dangerous situation would go to worse. Therefore, the dam safety monitoring and early warning is particularly important. The significance of the earth dam monitoring is explore and find hidden dam leakage quickly and efficiently, and reinforce the earth dam with a purpose.Due to fine linearity between the optical fiber and changes of the temperature and the stress that applied on the fibers, the method of using optical fiber to monitor the seepage and the settlement of dams has been proposed abroad. The force of the optical fiber and optical cable has been studied for the strength of optical fiber sensors application problems in the deformation monitoring system based on distributed optical fiber sensing. The relationship between the settlement stress and the physical quantities that direct impact the calibration of optical fiber in the practical application has been discussed to help for engineer application of optical fiber.The paper contains following contents:1. The domestic and international research literature have been synthesized. The background and the feasibility of real-time monitoring of the earth dam using distributed optical fiber sensors have been analyzed. The interaction of the optical fiber, the optical cable, its supporting structures and soil is preliminary studied when the distributed optical fiber sensing technology monitor the earth dams on line based on current force research of the optical fiber sensors.2. Aim at the force of optical sensing cable for a distributed optical fiber sensing monitoring system applied in embankment dams, concrete and other medium, a loading apparatus was designed. The commercial finite element analysis software Ansys 9.0 was applied to analyze the deformation of the optical cable in loading experiments, the relationship of optical cable strain and the load was got by analysis.3. The specific size and the material of the specific parts of the detecting deformation tube based on distributed optical fiber sensing were listed based on the principle of operation. The follow-up of the structure is designed based on specific engineering requirements. The strength and stiffness of the detecting tube were checked by using the ANSYS software.4. The force of the optical fiber and the light parth in the detecting tube were theoretical analyzed. The theoretical relationship between optical fiber strain and the depth of the detecting tube was obtained. The strain properties of the optical fiber was tested by the DiTeSt-STA202 analyzer.The modulus of elasticity is got by using the DiTeSt-STA202 analyzer as a kind of tight single-mode optical fiber for an example.5. The monitoring system of the detecting deformation tube based on distributed optical fiber sensing was built based on the DiTeSt-STA202 analyzer which produced by Omnisens company in Switzerland. The model of the detecting deformation tube and the earth dam model were founded in the ANSYA software. The contact pair between the tube and the soil was set up from the perspective of the interaction. The best laid location of the detecting deformation tube was found out by loading on the different location based on the different working condition. |
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