Experiment Study On Mechanical Properties Of The Interface Between Sensing Optical Fibers And Soils

In recent years, the application of distributed optical fiber sensing technology to field monitoring has become an important research subject in the field of geological and geotechnical engineering, but according to engineering practice, the deformation compatibility between sensing optical fibers and rock/soil masses will have great influence on the reliability of monitoring results. This problem always restricts the development of optical fiber sensing technology in engineering monitoring. Based on a series of laboratory pullout tests and time dependent pullout tests on soil-embedded optical fibers, the mechanical properties of the interfaces between different types of optical fibers and soils under various overburden pressures and the creep effect of optical fiber-soil interfaces were investigated. The analysis result indicate the mechanical properties of fiber-soil interface and stress-transfer mechanism, which provides valuable references for the application of distributed optical fiber sensing technology to soil deformation monitoring.The conclusions are as follows:1. This paper discusses the present situation and the existing problems about distributed sensing optical fiber application in rock and soil mass deformation monitoring.2. Based on the analysis of the deformation mechanism of distributed optical fibers embedded in soil masses, we design an optical fiber creep test device and a special fiber fixture.3. A quantitative analysis method of the deformation compatibility between a sensing optical fiber and soil is applied. Using this method, accurate and reliable test data can be obtained, and the deformation compatibility and stress transfer law of fiber-soil interface can be analyzed.4. The optical fiber pullout test results show that, with the increase of pullout displacement, the pullout force gradually increases at first. When the pullout force increases to the peak, it quickly reduces, and finally a residual pullout force is obtained. The simple model of pullout force-pullout displacement relationship can be used to analyze the whole pullout process.5. Through optical fiber creep test device, which can effectively obtain the creep data of optical fiber in the soil and can analyze the creep effect of the interface between optical fiber and soil under different conditions.6. By comparing the test results and detailed analysis, the results can provides us with effective references in engineering practice about the choice of optical fiber, layout scheme and judge whether the results of the optical fiber monitoring effectively.