42 5 ( ) Vol.42 No.5 2011 5 Journal of Central South University (Science and Technology) May 2011 Bragg 1 1 1 2 2 (1. 330099 2. 330038) ( ) D10 Bragg TU443 A 1672 7207(2011)05 1442 05 Fiber Bragg grating monitoring technology applied in soft ground settlement of highway LI Jian-hua 1, ZHANG Hong 1, LIU You-ping 1, ZHOU Yuan-fang 2, XIONG Mao-dong 2 (1. Department of Civil Engineering, Nanchang Institute of Technology, Nanchang 330099, China; 2. Jiangxi Highway Exploitation General Company, Nanchang 330038, China) Abstract: The fiber Bragg grating (FBG) technology was studied based on the current monitoring status of the highway soft ground settlement, such as the low degree of automation, the unsatisfied accuracy of the device, the slow data transmission and the greater measurement errors. The development of the long range optical fiber displacement sensor as well as its burying techniques which are suitable for soft ground settlement monitoring was analyzed. Both of them were applied in Dechang Highway D10 subject. The results show that the long-range optical fiber displacement sensor is able to meet the requirements of the soft ground monitoring. And data can be accurately monitored by means of real-time or on-line continuously. ey words: fiber Bragg grating; monitoring of soft soil foundation; long-range optical fiber displacement sensor; burying technology [1 11] FBG 2010 08 102010 10 28 (50969007)(2010BGB01302) (2010C00013 2010C00014) (1967 )13979123448 E-mail: gdwjljh@163.com
5 Bragg 1443 (Fiber Bragg grating) 1 1 3 1 4 FBG 1.1 FBG [12 15] T n eff 2 Bragg λ = n T (1) B 2 λ Bragg n eff B T Bragg T n eff Bragg λb = λb( 1 P e ) ε (2) P e ε Bragg λ B = λb( α + ξ ) t (3) α Bragg ξ Bragg t Bragg 1.2 FBG FBG FBG 20 cm 1 2 FBG 1 2 eff 1 Fig.1 Principle of long-range displacement sensor FBG1 1 13 = (4) 1 + 3 FBG2 2 2 4 = (5) 2 + 4 L FBG1 FBG1 ε 1 L ε 1 = (6) 1 L FBG2 FBG2 ε 2 L ε 2 = (7) 2 2 FBG 2 40 cm 1.3 FBG FBG FBG FBG
1444 ( ) 42 CFG 2.2 4 2 3.5 5.0 8.0 m 2~3 m MOI SI425 500 1 1.52~1.57 µm WMD 20 cm [16] 3 1 (JTGF 10 2006) 1 1 2 3 d 1 1 (2010 01~2010 05) 1 2 Fig.2 Installation of FBG displacement sensor m 3 Fig.3 Monitoring system of soft soil foundation 2 2.1 D10 0~3.5 m 3.5~5.0 m 5.0~8.0 m 8.0 m 1 Table 1 Parameters of displacement sensors / cm 1 15.0 / µm / (mm nm 1 ) 09219 1.549 964 89.825 316 09216 1.546 228 84.312 487 2 3.5 09218 1.557 828 98.021 470 3 5.0 09220 1.553 931 91.113 028 4 8.0 09514 1.544 756 84.816 678
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