埋地管道静载试验水平边界约束影响的数值分析

基于模型试验结果,通过有限元数值模拟软件研究静载作用下模型尺寸对埋地管道力学性能与形变性能的影响.数值分析结果表明:模型箱水平边界在距管壁20D以内变化时,随着模型尺寸逐渐增大,土体极限承载力不断增加,并且相同荷载水平下加载板沉降与管道径向变形比也随之变大,而管周土压力、管周径向和环向应力均随之减小,边界对管道的约束作用逐渐减弱;模型尺寸不同时,管道径向变形比在加载过程中的变化规律差异明显;地表静载作用下,管道以环向受压为主,并且由于管顶产生土拱效应,管周土压力中管侧处最大,管顶处次之,管底处最小;当模型箱外壁水平向扩展超出20D时,管道上方土体承载力、管道受力和形变规律基本一致.表明为减少或消除水平边界效应,模型箱外壁水平向扩展边界选20D为宜.

Numerical analysis of the effect of horizontal boundary constrains on the buried pipes under static loading

Based on model test results, the influence of model size on the mechanical and deformation properties of a buried pipeline under static load is studied by finite element numerical simulation software. The numerical results showed that when the distance between outside wall of the pipeline and horizontal boundary falls into the range of less than 25D(D, pipe diameter), the ultimate bearing capacity of soil gradually increases with the increase of the model size in horizontal direction.The variation regularity of pipeline radial deformation ratio in the process of loading is obviously different while the model size is different.Under the action of surface static load, the pipeline is mainly subjected to circumferential pressure. And due to the arch effect of soils at the top of the pipeline, the earth pressure around the pipeline reaches the highest at side of the pipeline, the second at top of the pipeline, and the smallest at bottom of the pipeline.Regularities for bearing capacity of the soils at top of the pipeline, for the force for the pipeline to take and for the deformation the pipeline maintain basically the same when the horizontal expansion of the outer wall of the model box exceeds 20D.