Study on Deformation and Offset Characteristics and Instability Range of Natural Gas Pipelines in Coal Mining Subsidence Areas

The study on the deformation and offset characteristics and instability range of buried natural gas pipelines in coal mining subsidence areas involves the interaction between mining-induced strata movement and natural gas pipeline structures. This research provides an important theoretical basis for achieving coordinated, safe, and efficient resource extraction in coal and natural gas resource overlay areas. Taking two buried natural gas pipelines in a coal seam mining area as the research objects, a main key stratum pipeline projection model was established. The deformation distribution and offset evolution characteristics of the pipelines were investigated, a control scheme for pipeline offset instability was proposed. The results indicate that the pipeline deformation distribution can be preliminarily analyzed through pipeline layout and the stage of coal seam mining. The active displacement zones of both the main key stratum and the pipeline layer exhibit an evolution pattern characterized by "horizontal O -shape, positive O -shape, and vertical O -shape". Pipelines with a large angle exhibit offset characteristics of "lag and advance", while pipelines with a small angle exhibit offset characteristics of "pseudo-advance and true conformity". The maximum pipeline displacement satisfies a logistic regression function with respect to the coal seam mining length. Based on curvature calculations, the pipeline instability range in the central section is determined to be 225 m. The offset instability range of Pipeline 1 is 658.5 m to 883.5 m, and that of Pipeline 2 is 306 m to 531 m. The pipeline offset instability center and offset instability range are related to the pipeline angle, the distance between the pipeline and the subsidence center, the length of the pipeline in the subsidence area, and the length of the pipeline deformation range.