Cross-fault Pipeline Monitoring Based On Coaxial Cable Large Strain Sensor

Fault is one of the most serious geological disasters faced by buried pipeline,which is easy to produce large deformations and lead to pipeline fracture damage,so it is particularly important to monitor large strains of cross-fault buried pipeline;The ground fissure activity under the fault causes great loss to the safety of human life and property,and the ground fissure monitoring has attracted the strong attention from scholars at home and abroad.Based on the large-scale,large-gauge and distributed monitoring mode of the coaxial cable Fabry-Perot Interferometer(CCFPI)sensor,the large deformation monitoring of the cross-fault pipeline and the real-time,long-term continuous monitoring of the ground fissure are realized by self-made fault soil box test device.The main work and research results are as follows:(1)According to the previous research on the sensing mechanism of the new coaxial cable sensor,the sensing principle and manufacturing method of the CCFPI sensor are described in detail,and it is applied from the laboratory monitoring sensor to the actual project-large strain monitoring of the cross-fault pipeline and the internal deformation monitoring of the ground fissures.(2)Starting from the demand for large strain monitoring of cross-fault buried pipeline,the applicability of CCFPI sensors is explored.First,the self-made cross-fault buried pipeline test device is used to simulate the stress state of the cross-fault pipeline in the actual project;Second,the packaging protection and layout method of applying the CCFPI sensor to the cross-fault buried pipeline is realized.CCFPI sensors and fiber optic sensors on the upper,right and lower sides to monitor the strain response state of buried pipelines to fault displacement;Finally,combined with the quantitative analysis of optical fiber sensor monitoring,qualitative analysis of ANSYS simulation and previous research results,the reliability of CCFPI sensor for large strain monitoring of cross-fault buried pipeline is proved from multiple perspectives,which provides a reference for its application in the monitoring of large deformation of pipelines under extreme natural disasters such as earthquakes and faults.(3)Starting from the demand for the real-time,long-term continuous monitoring of the ground fissure,the applicability of CCFPI sensors is explored.First,the ground fissures are formed by the self-made fault control model device to simulate the ground fissures caused by fault displacement in practice;Second,the encapsulation protection and fixed-point layout method of applying CCFPI sensors to the monitoring of internal strain and deformation of thesoil inside the ground fissures are explored,and the network laying method is adopted to monitor the internal strain and deformation at different locations inside the ground fissure;Finally,combining the fixed-point layout and network laying method used,the strain response and deformation of the soil inside the ground fissure are analyzed,and then the generation area of the internal ground fissures is predicted,and the cumulative width of the internal ground fissures is calculated.The CCFPI sensor at the same location was compared with the distributed optical fiber sensor to verify the rationality and effectiveness of CCFPI sensor monitoring the internal deformation of the ground fissure.