Research On Clinometer Technology Based On Fiber Bragg Grating For Simultaneous Measurement Of Cumulative Deformation And Sudden Deformation

In recent years,a great number of earth masses and mountain masses have been excavated due to the construction of expressway,railways and other infrastructure,thereby forming a great number of slopes.The landslides will be occurred easily when encountering thunderstorm weather,storm tide and human activities.Landslide disaster will cause tremendous deaths and injuries and property loss,so the slope safety monitoring is of great significance.However,traditional slope monitoring instruments are mostly electric inclinometer,which are easily interfered by electromagnetic fields and needs to record the data manually on the site of the slope.The degree of automation of this method is low and cannot achieve real-time monitoring.While,technology based on fiber Bragg grating(FBG)technology have many merits,including electromagnetic interference resistance,anti-corrosion,small size,light weight,remote monitoring,and multiplexing in series.Therefore,it has been widely used in slope monitoring in recent years.At present,the clinometer technology based on fiber Bragg grating is mainly used to monitor the cumulative deformation of the slope,but it is impossible to carry out timely monitoring and early warning for the overall movement or sudden deformation of the slope caused by special circumstances.In addition,most inclinometer devices cannot be taken out from inclinometer tube and reused once it is embedded in the slope,which leads to increased monitoring costs.In view of the above problems,this paper studies a clinometer technology based on fiber Bragg grating for simultaneous measurement of cumulative deformation and sudden deformation.The main work are as follows:(1)The methods of slope safety monitoring and sensing equipment were investigated,compared with various methods,summarized and analyzed the existing problems of some monitoring equipment.The preliminary design idea of sensors based on fiber Bragg grating was put forward according to these problems.(2)A clinometer based on fiber Bragg grating for simultaneous measurement of cumulative deformation and sudden deformation was designed,the temperature self-compensation method is used to solve the problem of temperature interference.The clinometers can be connected in series to achieve distributed measurement,and the interval and number of series can be adjusted according to the actual needs of project.The clinometers can be removed from the inclinometer tube for reuse when the monitoring is complete due to the shell of the clinometer is designed with wheel.(3)In order to obtain the full performance of the clinometer,the tilt calibration experiment,the vibration calibration experiment,the temperature compensation experiment and the creep-resistant characteristic experiment were carried out on the clinometer.The experimental results show that the tilt angle measurement sensitivity of clinometer is as high as 193.192pm/°,the vibration measurement sensitivity is 1565.544pm/g.In addition,the temperature compensation test experiment also manifests that the clinometer has good temperature compensation characteristics.In the creep-resistance experiment,the wavelength shift range of the output wavelength is only within 5pm,which is within the demodulation range of the FBG interrogator.This result fully indicates that the clinometer has good creep-resistant characteristics.(4)In order to verify the actual monitoring effect of the clinometer in the slope,a slope deformation simulation device and a displacement automatic measuring device with an accuracy of 0.02 mm were exclusively designed to carry out the deformation experiment.Three kinds of deformation model experiments were carried out,the experimental results show that the deformation displacement of the inclinometer tube monitored by the clinometers are consistent with the results measured by the displacement automatic measuring device,which verifies the feasibility and effectiveness of the clinometer.In addition,the vibration device was also designed to simulate the vibration caused by the sudden deformation of slope,and the vibration experiment is carried out.The experimental results show that the vibration data and the accumulated deformation data can be separated according to the rule,and the accumulated deformation information and vibration information can be obt ained by processing the separated data respectively,so as to realize the simultaneous measurement of the accumulative deformation and the sudden deformation.