Research On Monitoring Technology Andapplication Of High-steep Slope And Rockfall Based On Fiber Bragg Grating

Slope engineering is a common civil engineering in transport infrastructureconstruction. Collapse and falling rocks brought by slope instability especially highand steep slope often invade into traffic facilities, which is a grave threat to the safetyof national transportation business, and this problem becoming more and moreprominent with the rapid development of expressways and China RailwayHigh-Speed (CRH). Therefore, it is imperative to carry out an on-line safetymonitoring and early warning system for slope engineering. At present, the structurestates of slope are mainly measured periodically through the traditional electricalinstruments. Compare with the mechanical and electronic instruments, fiber Bragggrating technology based sensors have incomparable technical advantages. The signalof the FBG sensors is light, which is anti-electromagnetic interference and couldtransfer over great distances. Multiplex capabilities of gratings with differentreflection wavelength make it possible for a fiber to cascade dozens of measurementpoints. All these technical advantages make the FBG sensors suitable for the on-lineremote safety monitoring for large civil engineering in harsh environmentalconditions.With support fund from ministry of railways and China railway constructiongroup, new principle, new technique and new method of FBG sensing technology forthe key physical quantities of slope safety operation have been researched. Integratingthe theory design and engineering practice, the proposed monitoring method and thedeveloped FBG sensors have been used in the engineering field of slope and theimpact test of protective barrier.The FBG sensing method for distributed horizontal deformation of slope alongthe vertical depth direction is studied. A flexible bar model is made to carry out aseries of bending test. The actual deformation of the bar is accord with the resultdeduced by the theory of unit beam decomposition. To solve the defects ofinconvenience operation and unable to calibrate of traditional FBG anchor stresssensor, a novel FBG anchor stress sensor is designed and tested. According torequirement of surface displacement monitoring, a sloping structure based FBG displacement sensor has been designed and researched.Dynamic force and strain responses of protective barrier under the impact ofrock fall have been simulated by ANSYS LS-DYNA. A special elastic structure forforce transducer design has been researched. Two types of FBG force transducer weremanufactured based on the elastic structure. According to requirement of vibrationmonitoring, a cantilever based FBG vibration transducer with sensitization structureand a welding packaged vibration transducer based on metal-coated FBG have beendesigned and tested.FBG deformation sensors were mounted to the area of Diaoshuiyan slope whererecord a history of landslide to carry out online deformation monitoring. Theprocessing and analysis method for the deformation data of slope monitoring isdiscussed. The deformation monitoring data of Diaoshuiyan slope in several monthshave been analyzed and demonstrate that the two monitoring area is under the state ofunstable accelerating deformationTwo FBG displacement sensors were used to monitor the change of theexpansion joint of Diaoshuiyan Bridge. The FBG displacement sensors demonstrate astable performance, and the monitoring results consistent with the actual situation.FBG rock bolt sensors were used to monitor the anchorage force of a slope inGuiyang-Guangzhou railway.FBG force transducers, FBG strain sensors and vibration sensors were used inthe impact verification test of a rigid protective barrier. Dynamic force and strainresponses have been obtained effectively and consistent with the ANSYS dynamicexplicit results. Based on the results of dynamic explicit finite element analysis andthe impact test of protective barrier, five distinguishing models have been proposedand described in detail.