The Effect of Heterogeneous Backfill Soil on Leakage Behavior of Hydrogen-Blended Natural Gas Pipelines

Soil characteristics have a decisive influence on the leakage behavior of hydrogen-blended natural gas pipelines, the gas migration and diffusion laws, and the hazard range. However, existing studies are mostly limited to idealized and homogeneous soil conditions, failing to truly reflect the key restrictive role of the complex heterogeneity of backfill soil on the leakage and diffusion process. At the same time, there is a significant deviation between the diffusion mode of the leaked gas and the simulation results under normal homogeneous soil conditions. To obtain the physical property parameters of soil heterogeneity, this study adopted soil ring knife tests combined with the kernel density estimation (KDE) method for actual measurements, and used the heterogeneous soil parameters to modify the leakage model of buried hydrogenated natural gas (HBNG). The research results show that the heterogeneity of soil significantly affects the diffusion of leaked gas. The horizontal diffusion range of gas in backfill soil is 0.44 m higher than that in typical loam soil and 0.28 m higher than that in typical sandy soil; with the increase of hydrogen blend ratio (HBR), the mass flow rate of gas in backfill soil shows a downward trend; the average relative error between the gas mass flow rate prediction model established based on soil heterogeneity characteristics and the simulation results is 1.24%. The results of this study can provide numerical reference basis for the optimization of actual engineering schemes.