Failure characteristics of buried pipelines in subsidence areas under the influence of multi-adjustable factors during coal mining: A case study of Ordos, China

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Coal mining-induced ground subsidence often causes buried oil-gas pipeline failure. Insight the evolution of pipeline failure length and inflection points under the influence of adjustable factors (the distance between the panel pipe, panel width, internal pressure, and burial depth) has become increasingly essential for pipeline maintenance and operation. At present, the pipeline's failure length, failure time series, and inflection point distribution in subsidence areas are vague, which is not perfect in terms of specificity and clarity. Thus, a novel method to distinguish local failure and inflection points of pipelines is proposed by combining its moment and volume strain. Taking Panel 22102 of Ordos in western China as an example, the pipeline failure length and time series characteristics, as well as the inflection point spacing (IPS) are analyzed under the influence of adjustable factors by numerical simulation. The results show that (ⅰ) By increasing the distance between the panel pipe, and reducing the panel width, burial depth, and internal pressure, we can effectively mitigate or prevent pipe failures. For Panel 22102, the distance between the panel pipe should be less than 120 m to prevent failure. When it is unavoidable for the panel to pass underneath the pipeline, the width of the panel needs to be reduced to less than 120 m. (ⅱ) The pipeline failure length decreases by 2.9% for every 10 m reduction in the panel-to-pipeline distance. For every 10 m reduction in panel width, the pipeline failure length decreases by 5.7%. For every 0.1 m decrease in the burial depth, the pipeline failure length decreases by 2.16%. For each 1 MPa increase in internal pressure, the pipeline failure length increased by 0.48%. (ⅲ) The IPS is proportional to the panel width, burial depth, and internal pressure while exhibiting an exponential relationship with the distance between the panel and pipe. (ⅳ) The failure first spreads from the pipeline's subsidence center towards both ends, followed by spreading from both ends and the center towards inflection points simultaneously. (ⅴ) A multi-level and multi-faceted resilient management and collaborative operating pattern is established for the gas-coal integrated mining field. The research results provide scenario guidance and decision support for managers to develop adjusting measures to maintain pipelines, and also promote the coordinated mining of gas and coal resources.