关键词: 分层筑土, 非稳态泄漏, 扩散, 耦合, 模拟

Abstract: Urban gas pipeline network is mostly laid underground, which brings difficulties to detecting small leakage.After the leakage,it is prone to poisonous accidents such as poisoning, fire, explosion, etc., which brings hidden dangers to urban public safety.This paper sets up a calculation model for two backfilling methods of layered soil and non layered soil in pipe network,and different physical convection diffusion models are established for different laws of gas diffusion in soil and atmosphere environment.Based on the unsteady leakage model and the CFD software, the paper analysis the buried duffusion separately and analysis the atmospheric diffusion coupling soil and atmosphere.And the study about the effect of back filled soil on the diffusion of gas in soil and atmosphere.The results show that:low⁃ and medium⁃ concentration gas will delay diffusion and produce inflection point through stratified interface. The diffusion rate will increase after the layered interface, and the diffusion rate of gas in the layered soil will be high when the leakage time is greater than 100 s.The atmospheric diffusion rate of methane under stratified soil is not much different between the upwind side wind and the downwind directions. The longitudinal 100 s diffusion rate is larger than that one of the non stratified soil, and the larger the inertial resistance coefficient is, the faster the diffusion is.

Key words: Stratified soil, Unstable leakage, Diffusion, Couple, Simulation