Research On Slope Monitoring With Distributed Optical Fiber Sensing Based On Frame Beam Coupling

In recent years,road construction has been in a stage of rapid growth,so it is important for the safety monitoring of large-scale civil engineering.Due to the unique advantages of full-scale and continuous monitoring,distributed optical fiber sensing technology has great application potential in the field of geological monitoring.This thesis focused on the application research of distributed optical fiber sensing technology in slope engineering monitoring,and pointed out the limitations of distributed optical fiber sensing monitoring engineering at present:On the one hand,due to the limitation of spatial resolution based on BOTDR system,it is difficult to obtain actual strain,which easily causes low monitoring precision.In practical application,deformation or crack may occurs in a very short section.This requires superior spatial resolution to detect the strain and it may induce very large local strain which can easily break the optical fiber cable.On the other hand,the development of automatic slope monitoring system is based on the analysis of single parameter.FBG or Brillouin distributed sensing technology are mostly used for strain monitoring,but the vibration monitoring of the slope has been neglected.Vibration events may cause dynamic instability of the slope,and the superimposition of vibration may cause unexpected damage to the rock and soil structure.Therefore,the specific work of this thesis are as follows:(1)In order to fit for the slope monitoring,an optical fiber sensing structure(OFSS)for the distributed Brillouin optical fiber sensing network was developed.The OFSS composed of a PVC pipe and two pulleys,constructing multiple round-trips for the sensing fiber.The length of sensing fiber for short spatial length was extended significantly.So both the sensing accuracy and the tolerance to local deformation of the fiber are improved effectively.A comparative calibration experiment was designed in the laboratory to verify its performance with the spatial resolution of 1m.What's more,the effect of the proposed OFSS for landslide monitoring was confirmed through an on-site monitoring test on a shallow artificial slope.In addition,since the optical cable has no contact with the outside under the protection of the modified device,the survival rate of the cable is increased significantly.(2)This dissertation carried out on-site engineering monitoring project,and a monitoring plan for deep deformation,surface strain and slope vibration was developed.And then,the vibration alarm platform of the slope monitoring system based on C/S architecture was used for vibration monitoring of the slope.According to the characteristics of vibration signals,the appropriate threshold conditions was set.In order to know the vibration alarm for the first time,system can provide real-time alarm information to the mobile phone.In this dissertation,a double-parameter distributed optical fiber sensing monitoring technology scheme is proposed for the high slope monitoring project,which itegrates vibration monitoring into the slope monitoring.And a sensor structure is designed for BOTDR,both the sensing accuracy and the tolerance to local deformation of the fiber are improved effectively,which can provide a reference for the subsequent research.