Analysis on deformation and failure of buried pipelines during longwall coal mining

In recent years, the safety of oil and gas pipelines has been jeopardized by surface collapse which is caused by coal mining. In China, however, there are no mature standards on safety evaluation and stability quantification of buried pipelines above the goaf of coal mines. So far, no study has ever been carried out on pipeline deformation and failure characteristics that are presented at different stages of longwall mining. In this paper, the concept of safety factor was used to reflect the stress on different parts of the pipeline. Based on the fourth strength theory, the safety factor of pipelines was output by using the FISH language of the finite difference software FLAC^3D. Then, the stability of the pipelines was judged. And finally, analysis was performed on the change rules of safety factor and subsidence of the pipelines at different stages of longwall mining. The research results in this paper provide the theoretical basis for monitoring and protection of buried pipelines in subsidence areas.