油气管道极限压缩应变计算方法对比研究

Comparative Analysis on Methods of Calculating CSC of Oil and Gas Pipelines

埋地管道在通过不良地质地区时,如冻土区、活动断层区、采空区等,可能会产生较大的变形,影响管道的安全运行。对于管道应力已超过比例极限而管道继续变形的情况,基于应力的强度设计准则不再适用,针对此类情况通常采用基于应变设计。简要介绍了较早提出的UOA计算模型和相对较为新近提出的CRES极限压缩应变(CSC)计算方法,同时将其与DNV和CSA提出的CSC计算方法进行比照,从径厚比、内压、屈强比和几何缺陷四个方面将四种公式的计算结果与有限元结果进行对比,对比了各个极限压缩应变计算方法。UOA模型虽然考虑了几何缺陷,但适用范围较小。DNV模型过高地估计了内压对CSC的影响,适用范围也很有限。CSA模型结果在整体上偏于保守。CRES方法考虑的影响因素最为全面,适用范围也相对广泛,预测结果在整体上都与有限元结果一致,是目前几种管道极限压缩应变计算方法中适用性最好的一种。

Large deformation would be induced to the buried pipeline crossing the adverse geological zones, e. g. , frozen region, active fault zone and subsidence, which affect the safe operation of pipelines. For the condition where the pipe stress exceeds the proportional limit and the pipe keep on deforming, the stress-based design is no longer applicable, and it can be replaced with strain-based design. The previ-ously proposed UOA and relatively newly proposed CRES equations on CSC are provided. The models of UOA, DNV and CSA are compared to the CRES model. By the comparison in terms of the diameter-thickness ratio, internal pressure, yield-tensile ratio and geometry imperfec-tion with the four methods and FEM, the advance of CRES equations on CSC are analyzed and summarized. The geometry imperfection is considered in UOA model, but the parameter range is limited. DNV model overestimates the effect of internal pressure on CSC, and the range of parameters is limited. The results of CSA model are conservative. The CRES model recognizes the largest number of controlling pa-rameters, and the applicable range is relatively wide. The GRES results are in agreement with FEA overall. GRES is the most applicable model among existing models for calculating CSC.