Experimental Study On Suitability Of The Optical Fiber Bragg Grating Strain Sensor In Landslide Monitoring

China is a mountainous country.Tens of thousands of landslides and geological disasters occur every year,which cause huge economic losses and heavy casualties.In recent years,the average success rate of landslide prediction monitoring is only 3.88%.Therefore,we should further accelerate the research and development of landslide monitoring technology,improve the accuracy and ratio of landslide prediction,in order to reduce the hazards caused by geological disasters,and protect people’s lives and property safety.Deep displacement has been an important problem in landslide monitoring and research.The monitoring method based on borehole inclinometer has high precision and good effect,but there are many problems such as heavy workload and low automation.Fiber Bragg grating technology as a new type of engineering monitoring technology,Attention has been paid to researchers in engineering field,with its higher measurement accuracy,larger measurement range and resistance to electromagnetic interference,remote,automatic,real-time and so on.Based on this,this paper using fiber Bragg grating and ABS inclinometer tube made of fiber Bragg grating strain sensor(FBG sensor),supported by the National Natural Science Foundation of China(project number 51178488 and 51478066),the research work of this thesis is carried out.Through theoretical analysis,formula derivation and calibration test,model test and field application,proposed grating wavelength change value relation between landslide deformation,to study the suitability of FBG strain sensor in landslide monitoring,laid the foundation for the popularization and application of the sensor to the post.The main work completed in this paper is as follows:(1)Combined with fiber Prague grating sensing technology and borehole inclinometer,FBG strain sensor is designed.Based on the bending theory of fiber Prague grating sensing principle,beam and elastic anisotropic material mechanics principle,deduces the FBG strain sensor theory formula of center wavelength and the grating slope deep displacement sensor,describes the implementation process of slope monitoring with.(2)Through the FBG strain sensor indoor calibration experiment,the relationship between fiber Prague grating wavelength variation and the corresponding position of the grating strain sensor,get the experience formula of FBG strain sensor grating center wavelength and slope deep displacement;the theory of displacement and the displacement of the dial indicator FBG strain sensor using empirical formula obtained for comparative analysis,to verify the correctness of the empirical formula..(3)Landslide tests were carried out in the large model test cabinet made by the team,using the Composite Optic Fiber Transducer,inclinometer,FBG strain sensors to monitor the landslide deformation,comparative analysis of inclinometer displacement,composite fiber device,optical fiber loss changes the inversed displacement value and FBG strain sensor grating center wavelength change displacement inversion value of the relationship between the three,to verify the empirical formula of the Center FBG grating strain sensor and slope deep displacement of the rationality and reliability,also verified the composite fiber device before FBG strain sensor to design team has superiority in landslide monitoring,provides reliable basis for early warning and monitoring of FBG strain sensor.(4)Combined with the engineering geology situation,the FBG strain sensor is applied in engineering.Comparative analysis of inclinometer measuring displacement value and the center wavelength change value of inverse relationship between displacement value,not only verify the empirical formula of FBG strain sensor grating center wavelength and slope deep displacement of the rationality and reliability,also verified the FBG strain sensor technology for the feasibility and applicability of landslide monitoring field.