Effect of Longwall Mining on Exposed Pipelines: FEA Vs Measured Stresses

Abstract With coal and natural gas extraction often occurring in similar regions, pipeline operators are often forced to navigate the complexities of mine subsidence beneath their pipelines. Longwall mining operation has the potential to compromise the integrity of buried pipelines by creating high soil strains. Mitigation measures often include pipeline excavation and a strategic pipeline strain monitoring program to ensure that stresses on pipelines do not exceed allowable limits. In this research a comparison is made between the finite element analysis results versus measured strains in an exposed pipeline subjected to longwall mining subsidence in the Midwest. Strain gauges were attached to the exposed pipeline before subsidence was experienced to monitor changes in the strain throughout the duration of the subsidence event. Simultaneously, ground displacements were monitored by performing regular ground surveys. A soil-pipe interaction finite element model was developed to calculate pipeline strains based on calculated ground displacements using the Influence Function model. This paper compares the calculated strains from the finite element analysis to the actual strains measured by the strain monitoring system. Data from the case study are presented and compared.