Seite - 1432 - in Book of Full Papers - Symposium Hydro Engineering

The thermal field evolution law of unit 11 in 7 # section which bases on distributed optical fiber temperature measurement is displayed as Fig.10. From Fig.10, when there is no cooling water, the temperature of the upstream and downstream surfaces of the concrete are higher than the temperature at the middle of the concrete block at the age of 1 d. This condition is caused by low pouring temperature and hydration heat, simultaneously, the temperature of the upstream and downstream surfaces is affected by the environment temperature. At the age of 3d, the hydration reaction releases a large amount of heat and causes the temperature inside the concrete to rise sharply. At the age of 5d, under the effect of cooling water, the internal temperature of the concrete continues to rise, but the rate is slowing. When the age reaches 20d and above, the concrete temperature stabilizes at 24 to 26 ℃ and the temperature field distribution is more uniform. 5. CONCLUSION The distributed optical fiber temperature measurement system is developed to monitor and analyze the temperature change of low-heat cement concrete in Wudongde arch dam. The conclusions are as follows: Distributed optical fiber temperature measurement can achieve real-time online monitoring under the complex site condition and the monitoring accuracy can reach ± 1 C. Distributed optical fiber is alternately buried in the odd-even concrete block along the elevation direction and the "Z" shaped layout of optical fiber is used to enhance the accuracy of the temperature field reconstruction of the entire dam. At present, the monitoring results show that the internal temperature of low- heat cement concrete increases obviously under hydration action after placement without effect of cooling water. Then the temperature increases with the age at a steady rate under the control of cooling water. After it reaches the highest level (the temperature is controlled at less than 27 ℃), the temperature gradually decreases with the age and finally becomes stable under the cooling rate of less than 0.5 ℃ / d. The temperature distribution of the concrete will tend to be uniform. 6. REFERENCES [1] Bamoski M K, Jensen S M. Fiber Wavegaides: A Novel Technique for Investigating Attenuation Characteristics[J]. Appl Opt, 1976, 15(9):2112-2115. [2] Hartog A H. A distributed temperature sensor based on liquid-core optical fibers[J]. IEEEJ Lightwave Teclmol,1983(I):498-509. [3] Dakin J P. Distributed anti-stokes ratio thermometry, 3rd Interuational Conference on Optical Fiber Sensor, Postdeadline Session, San Diego, USA, 1432