黄土湿陷过程下埋地油气管道力学行为有限元模拟

针对黄土遇水后湿陷产生陷穴并引起埋地管道悬空这一过程中管道的力学行为，以基于弹塑性地基的黄土湿陷区悬空管道力学模型为基础，从湿陷原因和机理出发，建立三维有限元实体模型，模拟了土体湿陷过程和沉降变形，模拟计算结果与理论值和实测值进行了比对验证；进一步的计算和回归分析得到了管道最大位移、最大von Mises应力与地表土体湿陷沉降量的变化规律，同时也得到了最终湿陷情况下管道的von Mises应力分布和湿陷区范围的影响。结果表明:土体湿陷沉降是管道和土体共同作用的结果，湿陷前期管道与土体一起运动，位移和应力增加较快，而管道下方土体脱离管道产生陷穴后则增长较慢；管道最大位移和土体湿陷沉降量间呈对数函数关系，而管道最大von Mises应力和土体湿陷量呈指数函数关系； 湿陷区管段向下弯曲变形会在3个位置形成应力集中区，湿陷区范围增大会引起管道应力和变形的明显增加，且3个区域的最值分布有所不同。

Finite element simulation on mechanical behavior of buried oil/gas pipeline in loess collapse process

Aiming at the mechanical behavior of buried pipeline during its suspending process caused by sinkhole resulted from loess collapse when encountering water, on the basis of the mechanical model for suspending pipeline in loess collapse area based on elastic-plastic foundation, a three-dimensional finite element solid model was established considering the reasons and mechanisms of collapse. The collapse process and settlement deformation of soil were simulated, and the simulation results were compared and verified with the theoretical solutions and the measured values. The variation laws of the maximum displacement, the maximum von Mises stress of the pipe and the settlement amount of surface soil collapse were obtained in further simulation and regression analysis, and the influence of the von Mises stress distribution of the pipe and the range of collapse area under the situation of final collapse were obtained. The results showed that the settlement of soil collapse is the combined effect of pipe and soil. In the early stage of collapse, the pipe and soil move together, and the displacement and stress increase rapidly, while when the sinkhole occurs after the soil under the pipe separating from the pipe, the increase of the displacement and stress are relatively slow. The maximum displacement of the pipe presents a logarithmic function relationship with the settlement amount of soil collapse, while the maximum von Mises stress of the pipe presents an exponential function relationship with the settlement amount of soil collapse. The downward bending deformation of the pipe section in the collapse area will cause the formation of stress concentration areas in three positions, the increasing range of collapse area will cause the obviously increasing stress and deformation of pipe, and the distribution of the maximum values in three areas are different.