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The layout of urban buildings is concentrated and the height of buildings is ultra-high. Leakage accidents of urban natural gas pipelines caused by third-party construction damage occur frequently, which may cause serious accident hazards in construction areas. Simulation of the diffusion after gas leakage between buildings is necessary. Based on the characteristics of various urban layout forms, fluent was used to simulate the leakage and diffusion of natural gas pipelines under four different building layouts. The gas diffusion characteristics under different architectural layouts were explored, and the danger zone was summarized. The simulation results show that the enclosed layout is the most dangerous layout among the four types of layout. Within the building complex, natural gas diffusion at the near end of the leakage source develops from the bottom up, while natural gas at the far end of the leakage source settles from the top down and accumulates under the influence of vortex. The blocking effect of the building on the diffusion of natural gas leads to the accumulation of natural gas on the windward side of the building wall, and the dangerous area of natural gas appears on the outside wall and the top of the building. This study is of great significance to guide the prevention and reduction of natural gas accidents. [ABSTRACT FROM AUTHOR]

In order to analyze the effect of pipeline-soil action on the gas pipeline crossing under the soil landslide, the pipeline route selection in the landslide affected area was discussed. Based on smooth particle hydrodynamics and finite element coupling method (SPH-FEM), the force analysis model of pipeline under landslide was established. From the design point of view, the position of pipeline laying was comprehensively considered, the influence of pipeline wall thickness, buried depth and other factors was discussed, and the force deformation characteristics of pipeline under large soil deformation were analyzed. Based on the results, some suggestions are provided for pipeline routing optimization in landslide area. Results show that for the thrust-type landslide, when the pipeline is laid in the sliding mass, the stress and displacement of the pipeline at the leading edge of the sliding mass are small, and the damage of the pipeline at the posterior border is more likely. When the thickness of the pipeline wall is increased, the bearing capacity of the pipeline can be effectively improved, but with the increase of the buried depth, the effective yield strain of the pipeline increases first and then decreases. When the pipeline is laid outside the landslide, the stress of the pipeline located at the leading edge of the landslide is less than that at the posterior border, and it presents different stress states, which meet the safety of operation. At the same time, the increase of wall thickness can reduce the stress of the pipeline. The conclusions can provide suggestions for pipeline routing optimization in landslide area in the design stage, which has certain engineering significance and application value. [ABSTRACT FROM AUTHOR]

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