Dynamic Response Study Of Buried Pipeline Subjected To Blast Loads

With the rapid development of China's economy,pipeline transportation has developed rapidly because of its unique advantages and irreplaceable.By the end of 2016,China's natural gas pipelines have been built to about 68,000 kilometers,and it is expected that by 2020,the total number of natural gas pipelines in China will reach 104,000 kilometers.With the continuous improvement of China's oil and gas transportation pipeline network,the parallel laying of two or more pipelines is unavoidable,and the mileage of parallel pipelines will continue to rise.Taking account of the gradual advancement of urbanization construction,the distance between pipelines may be compressed smaller and smaller,and the impact of oil and gas pipeline explosions on adjacent buried pipelines will also become increasingly apparent.Therefore,it is becoming more and more urgent for the anti-burst performance of buried pipelines to propose relevant protective measures.At present,the domestic numerical simulation study of explosion impacts on pipelines adopts the ALE method.This method has the problem of unclear interface between flowing materials.It can not pay attention to the effect of soil compression and pipe slippage on pipeline stress.In addition,there is little research on dynamic response of defective pipe under blast loading.In this paper,a SPH-FEM coupling model,which is different from the traditional numerical simulation method,is applied to study the dynamic response process of parallel natural gas pipeline when the buried natural gas pipeline explode.Through the research and analysis,we got the following conclusions:(1)comparing with the experimental results,it was proved that the simulation calculation method of explosive impact in the specified medium was reasonable,and the design of SPH-FEM coupling model,algorithm,boundary condition and material parameter was reliable.(2)By setting up an actual working condition example to simulate,we evaluated the physical explosion impact of a buried parallel natural gas pipeline.The detailed analysis of the dynamic response process of the pipeline showed that the maximum stress at each point on the pipeline section was not symmetrical along the horizontal line,and the maximum stress on the implosion surface gradually migrated downwards over time;(3)Based on simulation analysis of different explosion distances,TNT equivalents,pipeline defects,and different soils,the study found that the maximum equivalent stress of the pipeline decreased exponentially with the increase of the explosion distance,increased linearly with the increase of the TNT equivalent and the depth of the defect,and we fit the corresponding function expression.At the same time,stress concentration would occur at the defect,and only a large equivalent stress could be generated under the effect of internal pressure.Under the impact of the blast,the high stress of the defect lasts longer.The stress of pipelines in different soils also differs greatly.The dynamic response of pipelines in sandy soil,loess and clay increases in turn.In the end,the entire research work was summarized and the future research directions were prospected.