Research On Pipeline Stability In Landslide Area Based On Finite Element Method

Oil and natural gas is a strategic resource to ensure the smooth development of the national economy and an important force for promoting social development.With the rapid development of China's oil and gas industry,domestic oil and gas pipeline networks are criss-crossed,oil and gas pipelines are built in batches,and pipeline transportation plays an irreplaceable role.The fast-growing pipeline industry is also facing severe challenges in terms of safety operations,especially the losses caused by pipeline geological disasters such as landslides,mudslides and collapses.In recent years,pipeline instability caused by landslide disasters is one of the most serious threats to buried oil and gas pipelines.It is of great engineering significance to study the stability of oil and gas pipelines in landslide geological disasters.Based on the finite element method and the theory of buckling eigenvalues,the relationship between various parameters of pipe and soil and pipe stability is quantitatively studied.For the pipelines crossing the landslide section,the pipe outer diameter,outer diameter wall thickness ratio,landslide width,landslide soil friction angle and landslide soil cohesion are taken as the research variables to quantitatively analyze the displacement,stress and buckling characteristics of the landslide disaster.The results show that increasing the outer diameter of the pipeline can effectively restrain the displacement of the pipeline during the landslide disaster.At the same time,as the outer diameter of the pipeline increases,the maximum displacement of the pipeline shows a quadratic curve,and the smaller the outer wall thickness ratio,the smaller the displacement increment of the pipeline.The maximum stress of the pipeline during landslide hazards occurs at the center and both ends of the landslide.Taking the outer diameter of 0.965 m as an example,the buckling characteristic value analysis shows that as the wall thickness ratio of the pipe increases,the buckling characteristic value decreases quadratic curve.With the increase of the outer diameter of the pipe,the buckling characteristic value increases linearly.With the increase of the internal friction angle,the buckling characteristic value decreases linearly.With the increase of soil cohesion,the buckling characteristic value is wavy.The buckling position of the pipeline occurs at the middle and both ends of the landslide section,and the ultimate landslide width that the pipeline can withstand is about 70 m.For the buried oil and gas pipelines that traverse the landslide section,the engineering pipeline stress was studied by taking the outer diameter of the pipeline,the wall thickness of the pipeline,the inclination angle of the landslide section,the length of the landslide section,the internal friction angle of the soil,and the soil cohesion.The structural stability of the engineering pipeline was analyzed with the variation of parameters.The results show that the maximum stress of the pipe appears at the elbow.The pipe stresses with outer diameters of 0.508 m,0.610 m,0.711 m,0.762 m and 0.813 m show a decreasing trend.As the outer diameter of the pipe increases,the maximum stress at the elbow shows a quadratic curve.Increasing the diameter of the pipe in the range increases the rigidity of the pipe and can effectively mitigate the impact of landslide disasters.Moreover,the maximum stress difference ratios at the upper and lower elbows of different pipe diameters are: 59.6%,56.6%,53.6%,51.9%,and 49.8%,respectively,indicating that the tensile stress at the top bend of the landslide is the key to disasters.Link.For pipes with a wall thickness of 0.0079 m,the stress at the top end of the landslide is significantly larger than the pipe thicknesses of 0.01 m,0.0159 m,0.0175 m,and 0.019 m.With the increase of the wall thickness,the stress at the elbow is reduced by 67.4.%,85.4%,27.65%,8.6%,indicating that increasing the wall thickness can improve the stability of the elbow.