Study On Fiber Optical Materials, Components And Smart Rock Bolt Structure

Smart materials and structures is a new field of material technology that develops rapidly in recent years. It is also a new discipline in high-tech material field. It is the advanced material in 21st century and the international development front of Engineering Science. Smart materials and structures is a cross-discipline. Its development is not only the demands of material science, but also the development requirements of other related disciplines and national economy.Based on the discussions about the recent development of fiber optical based smart materials and components, as well as the status of fiber optical sensor studies and applications, the concept of smart rock bolt is put forward according to engineering requirements. Following this concept, two kinds of practical structures of distributed strain sensors are brought forward upon the modulation principles of optical fiber micro-bend and fiber Bragg grating. In the mean time, the fundamental principles of these two types of fiber optical strain sensors are reviewed.In order to systematically evaluate the process technics, sensing ability to strain and application techniques of the suggested distributed micro-bend strain sensor adopting the winded structure of optical fiber around a small-diameter steel wire rope, some tensile tests of sensor and 3-point bend tests of concrete beams were conducted. The experiment results show that this kind of distributed strain sensor has good sensing property and high sensitivity. It can effectively identify the internal cracks of structure that occurs when the tensile stress exceed the tensile strength. Therefore it can be practically used for the real-time monitoring of rock bolt. This will make the rock bolt intelligent.Photosensitivity in Ge-doped optical fibers and high pressure HI loading as a technique for achieving ultrahigh UV photosensitivity is briefly discussed. 1300 nm FBGs were produced by using phase mask and KrF excimer laser on the Hi-loaded single-mode optical fibers. The strain and temperature sensing properties of FBG were discussed based on coupled-wave theory and elastic mechanics theory. Experiments were conducted to perform the study on their strain and temperature sensing characteristics. The tensile tests of rebar and bend tests of armor plates show that the produced FBGs have very good strain sensing attributes. The developed strain sensors using FBGs have good linearity, coincidence and high sensitivity.On the basis of above theoretical analyses and experiments, two kinds of smart rock bolt structures that based on distributed micro-bend strain sensor and FBG are put forward. The smart structures that take design, construction and monitoring of rock bolts as priority is suitable for application in rock bolt engineering.