Numerical Simulation Study on Methane Transport and Dispersion in Soil under Different Leakage Locations

Abstract

To further investigate the influence of leakage direction in buried pipelines on gas diffusion within soil, this study develops a fluid–solid coupled numerical model based on the unified Darcy–Brinkman–Biot equations. The migration behavior of methane and crack evolution characteristics under single-side, adjacent double-side, and three-side leakage conditions are systematically simulated and compared. The results show that leakage direction directly determines the geometric configuration of soil cracks by altering the initial kinetic energy distribution and local gas pressure. As the number of leakage directions increases, the number of cracks increases significantly; however, due to energy dispersion, the length and width of individual cracks decrease. The three-side leakage condition exhibits the highest peak pressure in the initial stage (exceeding 3700 Pa), which drives the formation of a more complex and dispersed crack network. In addition, the evolution of methane concentration fields is highly consistent with crack development. As the main cracks penetrate the boundaries and form stable flow channels, the gas transport mechanism transitions from pore diffusion to rapid transport along crack pathways, exhibiting a pronounced channeling effect. These findings provide important numerical evidence for urban pipeline safety monitoring and risk assessment.