Real scenario analysis of buried natural gas pipeline leakage based on soil-atmosphere coupling

Buried pipeline is the most common mode of natural gas transportation. The analysis of methane diffusion characteristics in leakage accident is of great significance for accident detection and secondary explosion accident prevention. The existing numerical simulation and experimental studies focused on the diffusion of methane in the soil from the leakage of buried natural gas pipeline, and the coupling process of methane passing through the soil and entering the atmosphere was rarely mentioned. However, the surface atmosphere is the main area of human activities, which increases the possibility of fire and other risk factors. In this paper, the coupling process of methane leakage passing through soil and entering the atmosphere was studied by numerical simulation, and the effects of various factors on the methane concentration in the first danger zone (FDZ) and the second danger zone (SDZ) were analyzed. Based on the least square method and multiple regression theory, combined with MATLAB mathematical calculation software, a methane concentration prediction model on the high-risk side of the FDZ was established. The results showed that after methane entered the atmosphere, the diffusion velocity increased significantly. The downstream building surface of the FDZ was the high-risk side of methane distribution, and the upstream building surface of the SDZ was the high-risk side. The average calculation error of the methane concentration prediction equation on the high-risk side of the FDZ was 9.97%, which can effectively evaluate the methane concentration under any leakage working condition. When the buildings floors were different, the high building surface between high building and low building was the high-risk side of methane distribution. This study provides guidance for the design of buried natural gas pipelines in residential buildings, and supplies basis for improving detector installation and gas leakage maintenance specifications.