青藏高原移动冰丘引起输油管道拱曲的数值模拟

青藏高原北部常年冻土区沿活动断裂发育有移动冰丘,其对输油管道、桥梁、涵洞等工程设施具有破坏作用。应用ANSYS有限元通用程序,对移动冰丘引起的输油管道的破坏进行了三维非线性有限元数值模拟计算,揭示了移动冰丘冻胀产生的应力场、位移场与塑性变形,给出了移动冰丘冻胀导致输油管道拱曲变形及应力分布。移动冰丘导致输油管道拱曲变形,在管道内部产生的应力超过管道的强度,使管道产生塑性弯曲变形和破坏,导致输油管道局部报废。移动冰丘导致输油管道拱曲变形的三维有限元数值模拟能够为管道工程设计和地质灾害防治提供依据。在数值模拟的基础上,提出了灾害防治措施。

Numerical modeling of oil pipeline bending caused by migrating pingos in the permafrost on the northern Qinghai-Tibet Plateau

Migrating pingos are developed along active faults in the permafrost area on the northern Qinghai-Tibet Plateau. They may destruct oil pipelines,bridges and culverts in the area. 3D nonlinear finite-element numerical modeling is performed of the destruction of oil pipelines by using the ANSYS finite element general procedure. It reveals the stress field,displacement field and plastic deformation caused by freezing and expansion of the migrating pingo and presents the oil pipe bending deformation caused by the migrating pingo and stress distribution. Bending of pipes produces compressive stresses of -515 MPa and tensional stress of 520 MPa inside the pipes,which exceed the yield strength of 450 MPa for the pipes,thus leading to plastic deformation and destruction of the buried oil pipes. The modeling of oil pipeline bending caused by the migrating pingo may provide an important basis for pipeline engineering design and prevention and control of geohazards produced by the migrating pingos in the study area. Finally measures of prevention and control are proposed.