走滑断层错动下采用抗拉拔承插式接口埋地管线力学性能及破坏机理

Mechanical behavior and failure mechanism of buried pipelines with anti-pullout bell-socket joints under strike-slip fault dislocation

断层位错下供水管线的破坏形式主要集中在管道接口等管线结构力学性能薄弱环节。在传统供水管线承插式接口的基础上引入橡胶垫圈和金属限位环进行优化改进,提出一种新型抗拉拔承插式接口,在达到正常使用极限状态前可发生一定拉压和转动变形;当接口轴向变形达到一定变形后,发生自锁现象阻止接口发生进一步拉脱破坏;自锁后的接口带动相邻管段与土体发生相对运动,形成锁链效应,从而有效吸收断层错动引起的管线过渡变形。为了研究采用新型承插式接口供水管线抵抗断层错动的能力,针对管道埋深、管道-断层夹角等关键因素,通过建立三维非线性管-土相互作用有限元模型进行深入分析,结果表明:采用新型承插式接口的管线其抵抗断层大变形错动的能力提高了近4倍,其失效模式由普通承插式接口的拉拔破坏转为接口的弯曲破坏;对于采用新型承插式接口的管道,其在管线-断层夹角为120°左右并且浅埋的情况下,其抵抗断层错动的能力提高最明显;有效的提高管道接口的轴向拉伸承载能力是提高承插式管道抵抗场地大变形能力的关键。

The damage of water-supply pipelines under fault rupture primarily concentrates at the pipe joints,which are the weakest structural links of the pipelines.Based on the traditional bell-socket joint of water supply pipelines,the rubber gasket and metal limit ring are introduced in the joint configuration,and a new type of anti-pullout bell-spigot is proposed.The new joint allows certain tensile-compressive and rotational deformations before the service limit state under daily operation.When the axial deformation of the joint reaches a certain level,a self-locking mechanism is triggered to prevent the joint from the pullout damage.The self-locked joint in turn leads to the relative movement between the adjacent pipe segments and the surrounding soil,and forms a chain effect,which effectively overcomes the excessive pipeline deformation caused by the fault dislocation.To assess the performance of water-supply pipelines incorporated with the proposed anti-pullout bell-spigot joint under strike-slip fault,the influences of the critical factors such as pipeline burial depth and pipeline-fault angle are investigated based on the numerical analyses of a three-dimensional nonlinear pipe-soil interaction finite element model.The results show that the pipelines incorporated with the anti-pullout bell-spigot joint can accommodate a strike-slip fault displacement 4 times of that for a traditional joint,and its failure mode of the joint changes from the pull-out failure to the excessive bending one.Moreover,for a shallowly buried pipeline with a fault crossing angle of 120°,the proposed joint can most effectively improve the resistance of the segmented pipelines against strike-slip fault movement.Overall,improvement of the axial tensile bearing capacity of the pipe joint is the key to improve the performance of segmented pipelines subjected to large ground deformation.