This paper presents a novel fiber-Bragg-grating- (FBG-) based system which can monitor and analyze multiple parameters such as temperature, strain, displacement, and seepage pressure simultaneously for forecasting coalmine water inrush disaster. The sensors have minimum perturbation on the strain field. And the seepage pressure sensors adopt a drawbar structure and employ a corrugated diaphragm to transmit seepage pressure to the axial strain of FBG. The pressure sensitivity is 20.20？pm/KPa, which is 6E3 times higher than that of ordinary bare FBG. The FBG sensors are all preembedded on the roof of mining area in coalmine water inrush model test. Then FBG sensing network is set up applying wavelength-division multiplexing (WDM) technology. The experiment is carried out by twelve steps, while the system acquires temperature, strain, displacement, and seepage pressure signals in real time. The results show that strain, displacement, and seepage pressure monitored by the system change significantly before water inrush occurs, and the strain changes firstly. Through signal fusion analyzed it can be concluded that the system provides a novel way to forecast water inrush disaster successfully. 1. Introduction As is known, FBG sensors are light weight, small size, easy to install, durable, corrosion resistant, water-proof, immune to electromagnetic interference, and so forth [1–3]. Furthermore, FBG sensors can be used to monitor large structures thanks to the inherent capability of multiplexing many sensors, which allows the measurement of several parameters at different places. In addition, FBG system can be employed as real-time monitor. Because of these intrinsic natures, FBG sensors are excellent for measuring static and dynamic measurement, such as temperature, strain, displacement, and pressure [4–9]. For FBG pressure sensors, pressure sensitivity is the main restriction. In [10] a novel FBG pressure sensor structure is proposed, which is based on a carbon fiber ribbon-wound composite cylindrical shell (CFRCCS). The sensor has a moderate measurement range (8？MPa) and high sensitivity (0.45？nm/MPa). Since FBG strain sensors are mostly encapsulated by stainless steel and other materials, they have an impact on the strain field of the surrounding rock or soil. Meanwhile, there are several kinds of FBG displacement sensors used in engineering, yet they are large in volume and imprecise. Therefore, continuing works on fiber sensors encapsulation are requisite. Meanwhile, FBG-based sensing systems have been employed in geotechnical engineering and model test
References
[1]
A. D. Kersey, M. A. Davis, H. J. Patrick et al., “Fiber grating sensors,” Journal of Lightwave Technology, vol. 15, no. 8, pp. 1442–1463, 1997.
[2]
S. Kim, S. Kim, J. Kwon, and B. Lee, “Fiber Bragg grating strain sensor demodulator using a chirped fiber grating,” IEEE Photonics Technology Letters, vol. 13, no. 8, pp. 839–841, 2001.
[3]
A. Iadicicco, A. Cusano, S. Campopiano, A. Cutolo, and M. Giordano, “Thinned fiber Bragg gratings as refractive index sensors,” IEEE Sensors Journal, vol. 5, no. 6, pp. 1288–1295, 2005.
[4]
Y. Zhan, S. Xue, Q. Yang, S. Xiang, H. He, and R. Zhu, “A novel fiber Bragg grating high-temperature sensor,” Optik, vol. 119, no. 11, pp. 535–539, 2008.
[5]
T. K. Gangopadhyay, M. Majumder, A. K. Chakraborty, A. K. Dikshit, and D. K. Bhattacharya, “Fibre Bragg grating strain sensor and study of its packaging material for use in critical analysis on steel structure,” Sensors and Actuators A, vol. 150, no. 1, pp. 78–86, 2009.
[6]
J. H. Ng, X. Zhou, X. Yang, and J. Hao, “A simple temperature-insensitive fiber Bragg grating displacement sensor,” Optics Communications, vol. 273, no. 2, pp. 398–401, 2007.
[7]
T. Guo, Q. Zhao, H. Zhang et al., “Temperature-insensitive fiber Bragg grating dynamic pressure sensing system,” Optics Letters, vol. 31, no. 15, pp. 2269–2271, 2006.
[8]
L. J. Cashdollar and K. P. Chen, “Fiber Bragg grating flow sensors powered by in-fiber light,” IEEE Sensors Journal, vol. 5, no. 6, pp. 1327–1331, 2005.
[9]
J. Wang, Q. Sui, D. Feng, and M. Jiang, “Novel FBG vibration sensor based on matching filter demodulation,” in Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, vol. 7283 of Proceedings of SPIE, pp. 251–256, May 2009.
[10]
D. Song, Z. Wei, J. Zou, S. Yang, E. Du, and H.-L. Cui, “Pressure sensor based on fiber Bragg grating and carbon fiber ribbon-wound composite cylindrical shell,” IEEE Sensors Journal, vol. 9, no. 7, pp. 828–831, 2009.
[11]
P. Ferdinand, O. Ferragu, J. L. Lechien et al., “Mine operating accurate Stability control with optical fiber sensing and Bragg grating technology: the European BRITE/EURAM STABILOS project,” Journal of Lightwave Technology, vol. 13, no. 7, pp. 1303–1313, 1995.
[12]
A. Kerrouche, W. J. O. Boyle, T. Sun, and K. T. V. Grattan, “Design and in-the-field performance evaluation of compact FBG sensor system for structural health monitoring applications,” Sensors and Actuators A, vol. 151, no. 2, pp. 107–112, 2009.
[13]
C. Li, Y. G. Zhao, H. Liu, Z. Wan, C. Zhang, and N. Rong, “Monitoring second lining of tunnel with mounted fiber Bragg grating strain sensors,” Automation in Construction, vol. 17, no. 5, pp. 641–644, 2008.
[14]
H. Zhu, J. Yin, L. Zhang, J. Dong, K. Fung, and W. Jin, “Deformation monitoring of dam model test by optical fiber sensors,” Chinese Journal of Rock Mechanics and Engineering, vol. 27, no. 6, pp. 1188–1194, 2008.
[15]
H. Li, H. Sun, Y. Liu, X. Sun, and Y. Shang, “Application of optical fiber sensing technology to slope model test,” Chinese Journal of Rock Mechanics and Engineering, vol. 27, no. 8, pp. 1703–1708, 2008.
[16]
T. Yang, C. Tang, Z. Tan, W. Zhu, and Q. Feng, “State of the art of inrush models in rock mass failure and developing trend for prediction and forecast of groundwater inrush,” Chinese Journal of Rock Mechanics and Engineering, vol. 26, no. 2, pp. 268–277, 2007.
[17]
D.-X. Cheng, Mechanical Design Handbook, Chemical Industry Press, Beijing, China, 2004.
[18]
B. Lee and Y. Jeong, “Interrogation techniques for fiber grating sensors and the theory of fiber gratings,” in Fiber Optic Sensors, F. T. S. Yu and S. Yin, Eds., pp. 295–382, Marcel Dekker, New York, NY, USA, 2002.
[19]
J. Wang, D. Feng, Q. Sui, and B. Liu, “Study of optical fiber Bragg grating seepage pressure sensor based on draw-bar structure,” Acta Optica Sinica, vol. 30, no. 3, pp. 686–691, 2010.
[20]
H.-W. Fu, X.-G. Qiao, and J.-M. Fu, “Studying on the plat metal diaphragm based fiber Bragg gratings pressure sensing,” Acta Photonica Sinica, vol. 33, no. 9, pp. 1119–1122, 2004.
[21]
W. Jing, L. Shu-cai, S. Qing-mei et al., “Study of FBG strain sensors based on similar materiel in zonal disintegration model test[J],” Journal of China Coal Society, vol. 37, no. 9, pp. 1570–1575, 2012.
[22]
L. I. Liping, Study on catastrophe evolution mechanism of karst water inrush and its engineering application of high risk karst tunnel [Ph.D. dissertation], Jinan, China, 2009.
