A Finite Element Model for Monitoring the Displacement of Pipelines in Landslide Regions by Discrete FBG Strain Sensors

Abstract

This study investigates a system for monitoring displacements of underground pipelines in landslide-prone regions. This information is an important alarm indicator, not only to prevent the failure of the line itself but also to mitigate the direct consequences of landslides on buildings and infrastructures in the affected area. Specifically, a numerical processing tool coupled with a data acquisition system is proposed. The starting point is the measurement of axial strain at three points of discrete sections of the pipeline by Fiber Bragg grating sensors, used to approximate the trend of mean axial strain and bending curvatures along the pipe axis. A finite element analysis based on a 3D geometrically exact beam model is developed for computing the deformed configuration corresponding to the input strain field. After assigning the boundary conditions, a mixed iterative scheme is used for a quick solution to the nonlinear problem. Firstly, the tool is validated theoretically with benchmarks on beam-like structures undergoing large deflections. Then, experimental results are produced on a monitored pipe buried in a wedge of land subject to an artificial slide. The overall sensor-modeling system, with zero displacements far from the landslide as a boundary condition, provides a satisfactory displacement trend with a mean error of about 18% with just three effective monitored sections in the affected pipe stretch of 18 m. The acquisition and processing tool is implemented in a web application as a real-time alarm system.