Analysis of Strain Sensor Cable Models and Effective Deployments for Distributed Fiber Optical Geotechnical Monitoring System

Abstract

Long range, distributed fiber optic sensing systems have been an available tool for more than a decade to monitor pipeline subsidence integrity challenges. Effective deployment scenarios are an important decision to be factored into the selection of this monitoring equipment and typologies relative to specific project needs. In an effort to analyze the effectiveness of various fiber optic deployment conditions, a controlled field experiment was conducted. Within this field experiment, a variety of distributed fiber optic sensors and point sensors were deployed in predefined positions. These positions relative to the pipeline were selected to support a range of deployment needs including new construction or retrofitting of existing pipelines. A 16-inch diameter by 60-meter long epoxy coated pipeline that was capable of being pressurized to mimic operating conditions was utilized. This test pipe was installed in a typical trench setting. Conventional point gauges were installed at key locations on the pipeline. Fiber optic sensor cables were installed at key locations providing 14 alternative scenarios in terms of sensitivity, accuracy, and cost. After construction of the test pipeline, real time continuous monitoring via the array of conventional and fiber optic sensors commenced. A deep trench was excavated adjacent and parallel to the central portion of the pipeline which began to induce subsidence in the test pipeline. Continued monitoring of the various sensors produced real time visualization of the evolving subsidence. A comparison of the reaction of the sensors is compiled to provide an intelligent selection criteria for integrity managers in terms of accuracy, deployment, and costs for pipeline subsidence monitoring projects. In addition, further analysis of this sensor data should provide more insight into pipeline/soil interaction models and behaviors.

Field Experience with DTSS based Geotechnical Monitoring: Lessons Learnt and Guidelines

“…• Distributed Temperature and Strain Sensing (DTSS) units based on stimulated Brillouin scattering, which is the preferred approach due to its long range capability [5]; each of these units is located in a pipeline node such as a pumping station; • Strain and temperature measurement cable sensors, respectively SMC and TMC; TMC also ensures the communication between stations and control centers ( [6], [7], [8]); • Data communication interface between monitoring units and the control centers including the use of the TMC cable; •…”

Detection of Pipeline Deformation Induced by Frost Heave Using OFDR Technology

“…In another case, Fabien Ravet et al [1] introduced an application of a distributed optic fiber sensor in a gas pipeline in Peru, and several events such as landslides and soil settlement were detected by strain measurement. Dana DuToit et al [11] conducted a realistic pipeline deformation test, where the fiber optic cables were mounted on the pipe and off the pipe, respectively. Test results showed that both on-pipe and off-pipe fiber optic cables provided valuable magnitude assessment of pipe deformations and strains.…”