Safety Study Of High Strength Steel Buried Pipeline Under Typical Geological Disaster

With the development of China’s natural gas usage increased year by year, natural gas buried pipeline especially high strength steel are long distance and span laying. The pipeline pass through many regions, where geological landforms is complex and changeable, the underground structure and potential hazards are difficultly to estimate, so the natural gas pipeline failure accidents take place frequently under geological disaster, caused huge economic losses and waste of energy, and even a threat to people’s life safety. Landslides, earthquakes and frost disaster in permafrost region is the most typical in many geological disasters. The above three kind of typical geological disaster are more frequent, more intense degree of hazard occurrence process, serious, extremely easy to cause the pipelines’ buckling deformation, stress concentration, and even rupture and explosion Therefore, research on the security of the high strength steel pipeline under typical geological disaster, have great significance for the analysis of the influence rules on pipeline safety factors, and the pipeline laying and maintenance.1. Two dimensional trench slope before and after excavation analysis models were established according to the actual working condition of landslide prone areas, and used to study on the stability of the slope; three-dimensional slope model were established for the stability analysis before and after adding anti-slide pile, the project was put forward to improve the stability of the slope. The mechanical behavior of pipeline under landslide was studied by the application of analytical methods; the displacement variation and stress of the pipeline under the action of the landslide are calculated by application of finite element methods, the results snowed that:the pipeline would be directly affected by the impact of the landslide body when the landslide disaster occurred, and the pipeline would have buckling deformation accompanied by a landslide fell, and with the increase of the slide displacement, pipeline deformation increased, then reached the yield limit, deformation gradually decreased. The pipeline would get into the stage of plastic deformation when exceeded the yield limit. The size of the landslide, slope angle, soil types and buried depth of pipe and other factors on pipeline safety were studied based on the previous research.2. Three dimensional analysis models of pipeline under the action of earthquake were established, viscoelastic artificial boundary and the seismic wave spectrum were brought to the models for calculation, the calculation results were analyzed. Pipelines’ axial stress increased with the increase of seismic peak acceleration, pipe diameter to thickness ratio and the pipe soil friction angle, and decreased with the increase of axial diameter, buried depth has little effect on the stress.3. The finite element models for the analysis of soil temperature and frost heave effects on pipeline in permafrost region were established through the analysis of test and frost heaving characteristics of soil frost heave mechanism, combined with the actual conditions, the safety of pipeline in permafrost regions by frost heaving was studied. Ppelines’ safety was analysed under different temperatures and different of pipeline buried depth. Pipelines’ floatation displacement and maximum stress were increased with the decrease of temperature, although did not achieve the ultimate yield of the pipeline, the perennial stress effect caused of temperature change and the influence of low temperature were likely to make the pipe to generate larger deformation; pipelines’ floating displacement decreased, but the maximum stress increased with the increase in depth.Safety of high strength steel buried pipeline under three kinds of typical geological disaster was studied in this paper, it was significant for pipeline laying and maintenance in the disaster prone areas.