保障中俄东线天然气管道长期安全运行的若干技术思考

针对中俄东线天然气管道的实际服役状况,分析了土壤运动(冻胀与解冻沉降)对管道结构完整性的影响以及基于管体结构-土壤弹簧模型在确定管-土交互作用方面的局限性,即非线性、大应变与多轴加载评估的保守性、土壤本构模拟与真实状况的偏离,建议发展新型多模块耦合集成技术确定土壤运动产生的机械效应。明确了X80高强管线钢在服役条件下发生应变时效及其导致管线钢(尤其是焊缝区)材料韧性和止裂能力的降低,建议使用时效活化能与等效时效时间模拟、评估管线钢在漫长服役过程中发生应变时效的敏感性,并建立相应的理论基础。此外,详细分析3种常见的管道缺陷(机械损伤、腐蚀缺陷、裂纹)对管道完整性影响的评估技术现状。针对高压、大口径、高强钢天然气管道(特别是焊接金属与热影响区)在地质不稳定地区的材料韧性、裂纹扩展以及止裂能力开展实验与评价技术,建立精确的多物理场协同作用下的管道缺陷评估模型,是当前的国际性技术难题,这些问题的解决将有力保障中俄东线天然气管道以及相关油气管道的长期安全运行。

Technical insights into the long-term integrity and sustainability of China-Russia Eastern Gas Pipeline

This work developed technical insights into the maintenance of integrity,safety and sustainability of the newly operated China-Russia Eastern Gas Pipeline,and beyond.The adverse effect of ground movement in permafrost and semipermafrost regions,typically frost heave and thaw settlement,on the pipeline structural integrity was analyzed.The pipe beam-soil spring model presently used by industry is not appropriate due to multiple limitations in modelling the pipe-soil interaction(i.e.,nonlinearity,conservative assessment of large strain and multiaxial loading,and non-realistic modelling of soil constitutive properties).An integrated technology framework was proposed to quantify the soil stress/strain generated during ground movement.Moreover,the strain ageing of high-strength X80 pipeline steel in the geologically instable region was mechanistically analyzed,where the toughness and crack arrcstability of pipe steel,especially the welding zone,would be degraded remarkably.It was suggested that the activation energy for straining ageing and the equivalent ageing time be appropriate for modelling and predicting the strain ageing behavior of X80 steel during the long-term service period in the field.Finally,the state-of-the-arts of the assessment models for mechanical damage,corrosion defects and cracks were reviewed,and the applicability of the modelling methods on high-pressure high-strength steel gas pipelines was discussed.It was recommended that research efforts be made on development of the testing and modelling methods for determination of the toughness and crack arrestability of the steel(especially the weld metal and heat-affected zone),as well as the technology for safety assessment of the target pipeline project.