Experimental Study On BOTDA Distributed Optical Fiber Monitoring Technology

With the rapidly development of China's economy and society,the infrastructure construction has expanded unprecedentedly.While a series of safety problems are often encountered in the process of construction,such as structural cracking,bending deformation and failure.In order to prevent the occurrence of major disasters in project construction,reasonable and effective monitoring means should be adopted to monitor the whole process of project construction.Distributed optical fiber sensing technology,with its advantages of high precision,good stability,anti-interference and strong durability,can achieve a wide range of long-distance and fully distributed monitoring in engineering.As a new monitoring method,it is gradually applied to engineering safety and health monitoring.However,optical fiber is a brittle material that can be easily bent and fractured,which makes it meet technical difficulties in the application of large deformation monitoring in rock and soil;Due to the limitation of field conditions,the identification,localization and accurate monitoring of micro-cracks by optical fiber also need further study.Based on BOTDA distributed fiber optic monitoring technology application in the geotechnical engineering disaster monitoring requirements,through the design of three kinds of the engineering application of laboratory test,the research of distributed optical fiber respectively in the geotechnical engineering monitoring need to solve the problem of three monitoring technology,is proposed based on BOTDA distributed optical fiber strain sensor technology supporting structure of large deformation monitoring technology,disaster monitoring tiny fracture identification technology and monitoring technology,for the BOTDA distributed optical fiber strain sensor is applied to the engineering disaster monitoring method provides support.The main research contents include the following aspects:(1)Based on the sensing principle and characteristics of DPP-BOTDA monitoring system,the pile supporting structure in the geotechnical engineering design of indoor test,connection method and the distributed optical fiber technology,was deduced based on BOTDA distributed optical fiber strain sensor test technology formula of displacement of supporting structure,carried out based on the technology of DPP-BOTDA distributed optical fiber beam supporting structure of indoor experiment,comparison and analysis of the distributed optical fiber monitoring displacement data and dial indicator test results,verify the accuracy of the test method,effectively gives the pile supporting structure of the distributed optical fiber measurement technology and the displacement analysis method.(2)Through the analysis of the tensile properties of DPP-BOTDA distributed optical fiber,designs the stock based on optical fiber coordinate deformation of large strain deformation test laboratory test methods and test equipment,analyzed the distributed optical fiber tensile stretch rate influence on deformation test precision,by conducting multiple sets of coordination of deformation testing experiment and study the more shares the deformation coordination of the fiber analysis method and continuous coupling between optical fiber strain analysis technology,gives the stock based on optical fiber coordinate deformation of small strain large deformation calculation method of the distributed optical fiber displacement,comparative analysis of the optical fiber displacement testing data and actual deformation value,The rationality and accuracy of the testing technology of large deformation of rock and soil based on small strain of optical fiber are validated effectively,which provides technical support for distributed optical fiber monitoring of geotechnical engineering disasters.(3)With high strain sensitivity characteristic of distributed optical fiber as the basis,design the laboratory identification,test,test of micro cracks,micro fracture control of auxiliary testing equipment is developed,has carried out several test point of view,different micro crack width of distributed optical fiber tiny crack test experiment,through the comparison and analysis of experimental data,and load deformation,put forward the precision of the identification accuracy of 0.1 mm,0.01 mm of distributed optical fiber tiny crack testing and monitoring technology,provides the concrete supporting structure of the geotechnical engineering test technical support.Figure[63]table[11]reference[53]...