基于频谱分析的地震带输气管道应力分析方法

Stress analysis of gas pipelines at seismic belts based on the spectrum analysis

地震是输气管道失效的重要原因之一,强烈的地壳运动带动土壤错动,载荷作用于输气管道上极易引起管道变形,而目前国内外对地震带输气管道的动态应力分析研究较少。为此,基于地震频谱分析方法,采用CAESAR II软件对XX地震带输气管道进行了动态应力分析,并校核了在强震作用下输气管道的位移、应力是否符合规范。结果表明:①轴向、横向、纵向及综合地震作用对输气管道的横向位移影响最大,且最大横向位移明显高于最大轴向及纵向位移;②地震作用下最大纵向位移和横向位移均产生在坡顶,设计时需重点对坡顶输气管道的位移量进行校核;③综合地震作用较任一单方向地震作用所产生的管道位移、应力更高,综合地震载荷对输气管道的破坏最大。据此提出建议:地震带输气管道设计过程中,可通过极限设计的方法提高输气管道的抗震能力且应重点对输气管道的横向位移进行监测,可通过改变管道敷设线路或减小土壤压实度的方法来控制输气管道的位移。

Crossing through seismic belts, gas pipelines are under the condition of soil rupture resulted from a strong crustal move- ment, which would easily cause pipe bending deformation. At present, both domestic and abroad oil and gas pipeline stress analysis is limited to static analysis, while dynamic stress analysis has not yet been touched upon. In view of this, based on the principle of seismic spectrum analysis, a pipeline dynamic stress analysis was performed by inputting spectral parameters of the pipelines cross ing through the XX seismic zone into the seismic analysis module of CAESAR II. The results indicated whether or not the pipeline displacement and stress under a violent earthquake action would conform to ASME B31.8 specification. The following findings were made. First, the radial, transverse, longitudinal and combined seismic actions has the biggest impact on the lateral displacement of gas pipelines; and the maximum lateral displacement is obviously higher than the maximum radial or transverse displacement. Sec- ond, under the seismic action, both the maximum transverse and longitudinal displacement occur on the top of slopes, which should be highly focused on in the design. Third, the displacement and stress caused by the combined seismic actions are higher than those by any single direction seismic action and the combined seismic load has the worst damage to the pipelines. Accordingly, we put for- ward the following proposals. The ultimate design method should be adopted to strengthen pipelines against earthquakes; the pipe lateral displacement should be highly monitored; and such measures as changing pipeline routes or reducing soil compaction degree should be taken to minimize the earthquake impact, thereby to control the displacement of gas pipelines.