管土耦合作用下超临界CO_(2)管道裂纹动态扩展模拟方法

The numerical simulation method for dynamic crack propagation of supercritical CO_(2)pipeline under the pipe-soil coupling

为解决现有流固耦合模型建模难度高、计算效率低而无法广泛用于CO_(2)管道裂纹扩展预测的问题,提出了一种基于减压模型的管土耦合作用下CO_(2)管道裂纹动态扩展模拟方法。在该方法中管道断裂与流体减压间复杂的流固耦合作用由基于爆破实验及模拟所得压力数据提出的CO_(2)三维减压模型结合加载子程序代替实现,大变形下管土耦合关系采用光滑粒子流方法描述。为验证所构建数值模拟方法的可靠性,将其用于再现管道爆破实验,同时基于该方法对半回填、无回填及完全回填状态下CO_(2)管道韧性断裂行为进行了对比研究。结果表明,所提出的模拟方法较为可靠,两种工况下裂纹扩展速度模拟值与实验值误差分别为21.6%与7.6%,证明所构建的减压模型可有效描述裂纹扩展过程中管内压力时空演化规律,同时可避免对复杂流固耦合问题的求解,为后续超临界CO_(2)管道断裂行为参数化研究及止裂预测模型的构建奠定了基础。研究结果表明,土壤回填效应对管道裂纹扩展长度、速度、管道整体变形等断裂行为影响显著,相较于无回填管道,完全回填管道裂纹扩展速度下降了19 m/s,且管道变形受到明显限制,有利于裂纹止裂。

To solve the problem that the existing fluid-solid coupling structure model cannot be widely applied for predicting crack propagation in CO_(2)pipelines due to its high difficulty in modeling and low computational efficiency,the paper proposes a simulation method for the dynamic crack propagation of supercritical CO_(2)pipeline based on a decompression model.In this method,the complex fluid-structure interaction between pipeline fracture and fluid release is achieved by a three-dimensional CO_(2)pressure decompression model combined with loading subroutines,which is first proposed based on pipeline pressure data obtained from full-scale burst experiments and numerical simulations.The coupling relationship between pipeline and soil under large deformation is described using the smoothed particle hydrodynamics(SPH)method.To verify the reliability of the proposed numerical simulation method,it is used to reproduce the pipeline burst tests;based on this method,a comparative study is conducted on the ductile fracture behavior of CO_(2)pipelines without backfill,with half and full backfill.The results indicate that the proposed method is reliable.The error between the simulated and experimental values of crack propagation speed under two working conditions is 21.6%and 7.6%,respectively,demonstrating that the established decompression model can effectively describe the space-time evolution of the pressure in the CO_(2)pipeline during crack propagation and can avoid solving complex fluid structure coupling problems,thus laying the foundation for the subsequent parameterization study of fracture behavior and the construction of crack arrest prediction models for supercritical CO_(2)pipelines.The research result also shows that soil backfilling has a significant influence on crack propagation length,velocity and whole deformation of pipelines.Compared with pipelines without backfill,the crack velocity of fully backfilled pipelines is decreased by 19 m/s,and the pipeline deformation is significantly limited,which is beneficial for crack arrest.