Numerical Simulation Analysis of the Impact of Forest Wildfire on Buried Pipelines

In recent years, forest fires have occurred frequently, and extremely high temperatures can easily cause plastic deformation of buried pipelines. To clarify the temperature-stress variation law of natural gas pipelines under wildfire action, this study, based on heat transfer theory and using the finite element method, constructs a numerical model of a buried pipeline and analyzes the thermo-mechanical sequential coupling behavior of the pipe–soil system. It elucidates the influence patterns of key factors such as burial depth, outer diameter, internal fluid pressure, soil thermal conductivity, and fire duration on the temperature-stress fields of the pipe and surrounding soil and investigates pipeline deformation under fire. The results show that burial depth is the most sensitive factor: when it increases from 0.2 m to 0.8 m, the maximum pipe temperature decreases from 291.4 °C to 32.4 °C, and the maximum von Mises stress decreases from 507 MPa to 236 MPa. Furthermore, increasing pipe outer diameter and soil thermal conductivity both exacerbate pipe temperature rise and stress accumulation. Meanwhile, the longer the duration, the more pronounced the soil heat storage lag. Additionally, when internal pressure increases from 2 MPa to 8 MPa, the pipe’s maximum stress increases by up to 10.8%. The analysis results can provide a theoretical basis for identifying high-risk pipeline sections and guiding route selection and protective measure optimization for pipelines crossing forested areas.