冻胀对含缺陷管道应力的影响研究

Study on the Influence of Frost Heaving on Defective Pipeline Stress in Frozen Soil Zone

为保障冻土区埋地管线在寒季的安全运营,针对中俄漠加段含腐蚀缺陷埋地管线寒季的冻胀灾害工况,采用ABAQUS建立冻土区三维热固耦合有限元模型,研究了冻胀区长度、缺陷深度、缺陷宽度及缺陷位置等对埋地管道内外壁双层面轴向应力的影响。研究结果表明:当土壤发生冻胀时,管道内、外壁面沿轴向会出现3个高风险失效区,外壁面风险失效区位于距冻胀区0~10 m的非冻胀区和缺陷区域,内壁面风险失效区位于距冻胀区0~5 m的非冻胀区和缺陷区域,内外壁沿轴向Von Mises应力对寒季地表温度敏感性极高,最高可达43%,因此寒季应根据冻胀区长度对高风险失效区管道进行适当补强;当且仅当缺陷位于冻胀区域中轴线时,冻胀将加大腐蚀缺陷处管道失效的可能性;缺陷域内管道内外壁最大Von Mises应力对缺陷深度最敏感,最高可达58%,对冻胀土壤长度、缺陷宽度和寒季温度较敏感,绝对值均达10%以上;各种因素与寒季气温变化多呈非线性关系且二者互相促进加速管道失效。研究结果可为寒季冻土区输油管道的完整性评价及维护检测等提供依据,具有一定的理论指导意义和工程实用价值。

To ensure the safe operation of buried pipelines in frozen soil areas in cold season,in view of the frost heave conditions of buried pipelines with corrosion defects in the Sino-Russian Mojia section,ABAQUS is used to establish a three-dimensional thermo-solid coupling finite element model for frozen soil areas,in order to study the influence of the frost heave zone length,defect depth,width and location on the axial stress of the inner and outer walls of the buried pipeline.The research results show that when soil frost heave occurs,there will be three high-risk failure zones along the axial direction on the inner and outer walls of the pipeline.The failure risk zone on the outer wall is located in the non-frost heave area and defect area 0~10 m away from the frost heave zone.The failure risk zone of the inner wall is in the non-frost heave area and defect area 0~5 m away from the frost heave zone.The axial Von Mises stress of the inner and outer walls is extremely sensitive to the surface temperature in cold season,which is up to 43%.Therefore,in cold season,the pipeline in the high-risk failure zone should be properly reinforced according to the length of the frost heave zone.Only if the defect is located on the central axis of the frost heave zone,frost heave will increase the possibility of pipeline failure at the corrosion defect.The maximum Von Mises stress of the inner and outer wall of the pipeline in the defect zone is the most sensitive to defect depth,which is up to 58%,and is also sensitive to frost heave soil length,defect width and cold season temperature,and the absolute value is more than 10%.Various factors and the temperature change in cold season have mostly nonlinear relationship and they promote each other to accelerate pipeline failure.The research results can provide a basis for the integrity evaluation and maintenance inspection of oil pipelines in frozen soil areas in cold season,and have certain theoretical guiding significance and engineering practical value.