| According to the data of the Minitry of Land and Resources of PRC, the pecent of slope geological disaster is 70% in all our country geological disasters (landslide, debris flow, subsidence, etc.) and remaineds high from 2010 to 2014. Slope geological disaster leads to huge casualties and economic losses every year which which seriously affects the production and living of our national security and restricts the rapid development of economic construction and social. Therefore, according to the characteristics of slope geological disaster, such as strong burst, wide distribution and certain concealment etc, comprehensive system research of slope geological disaster, especially human factors influence of slope geological disaster and build effective project monitoring technology and safety evaluation of forecasting system have great significance at timely discovering and putting forward corresponding disaster prevention measures, avoiding population missing or death, reducing the economic loss and improving the safety and quality of the national production and life. Due to its own characteristics, such as small volume, multiplexing capability, high precision, intrinsically safe, resistance to electromagnetic interference and easy to implement remote signal transmission, the fiber Bragg grating (fiber Bragg grating) provides a more effective way to solve slope geological disaster through several decades development. Due to that the slop geological disaster has the characteristics of burst strongly, wide distribution and concealment, the existing optical fiber Bragg grating monitoring technology has certain deficiencies in slope safety monitoring, such as few research work on grating area static/dynamic non-uniform strain effect and reconstruction, few multidimensional parameter detecting element at same time, simple later data processing, huge multiplex cost of the optical fiber Bragg grating monitoring system. All these deficiencies limit the application of the optical fiber Bragg grating monitoring system in the large geological engineering structure.Based on the above discussion, this paper chooses the slope geological disasters as the engineering object of the optical fiber Bragg grating monitoring system, selects sudden model experiment of under tunnel slope rockfall and slope creep landslide of the loess plateau as the engineering sample, studies the influences and reconstitution of grating area under non-uniform static/dynamic strain (theoretical analysis), designs the miniaturization and engineering fiber Bragg grating sensors which are suitable for the geological model test and engineering application (sensor development), applies the single processing technology to improve the detection precision of the grating sensors (performance optimization), uses the improved blind source separation algorithm to realize the multiplexing of the same wavelength optical fiber (network expansion) at one channel and finaly eastablises the optical fiber Bragg grating monitoring system and does some research on its slope engineering application performance (system integrated and applications). The main research work is as follows:1) The influences and reconstruction of non-uniform, especially the dynamic grating area strain is studied based on transfer matrix theory of fiber Bragg grating to guide the development of fiber Bragg grating detection element and realize the dynamic monitoring of slope disaster. ① the influence of non-uniform static stress on the the optical fiber Bragg grating reflectance spectrum is analyzed and further the dynamic non-uniform stress effect on the grating reflection spectrum is also analyzed based on wavelength range wide, relatively homogeneous linear chirp grating. ② in order to ensure the grating reflection data acquisition rate and provide data for heterogeneity stress reconstruction, compression sensing algorithm with far lower requirment than the Nyquist sampling theorem is introduced to realize the low sampling and high precision of full grating spectrum refactoring. ③ based on the analysis of non-uniform stress field and low sampling, high-precision full spectrum reconstruction, non-uniform grating area stress distribution reconstruction self-adaptive algrothm is proposed.2) Design principle of fiber Bragg grating sensor is proposed by according to the electricity sensor. The miniaturization (three-dimensional strain sensors with the same origin based on elliptic ring, micro fiber Bragg grating pressure sensor, micro fiber Bragg grating displacement sensor, etc.) and engineering (fiber Bragg grating anchor dynamometer, fiber Bragg grating displacement sensor with variable precision and wide range, discernible circumferential identification fiber Bragg grating tilt sensor) fiber Bragg grating sensors which are suitable for the geological model test and engineering application are designed and studied.3) The signal processing methods (wavelet transform, Duffing chaotic oscillator model, Hilbert-huang transformation) are introduced to obtain the static and dynamic information of fiber Bragg grating detection data and further improve the detection precision of the fiber Bragg grating sensor. The fiber Bragg grating sensor which can realize multiple parameter acquisition at same time is developed, such as flow velocity/temperature fiber Bragg grating sensor and fiber wrist vibration sensor with tilt, acceleration and temperature synchronous measurement.4) Based on the application limitations of the existing fiber Bragg grating multiplexing technology (wavelength division multiplexing, time division multiplexing, air division multiplexing) in the wide distribution monitoring of slope geological disaster, same fiber wavelength multiplexing at one channel is proposed based on the improved blind source separation algorithm and further verified by simulation and testing experiment. The multiplexing method extends the network scale of the fiber Bragg grating monitoring system.5) The fiber Bragg grating monitoring system is used in model experiment (underwater tunnel, slope rockfall model test of under wear tunnel) and engineering field (Lanzhou Black Table) and the real-time online monitoring of the dynamic slope deformation is realized. At its operation period, the monitoring system successfully forecasts the site condition of slope engineering. The common people are all timely and orderly evacuated and nobody loss. The slope application results which are displayed by China Geological Survey confirm that the fiber Bragg grating monitoring system has significant social and ecological benefit. |
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