基于弹性地基梁理论的冻胀作用下管道应力分析

Stress analysis of pipelines subjected to frost heave based on the theory of elastic foundation beam

穿越冻土区的埋地管线在遭遇冻土差异性冻胀时,管道会发生翘曲变形,管线将面临很大的安全隐患。为此,基于弹性地基梁理论建立冻胀条件下的管-土相互作用模型,分析了管道在冻胀及其影响因素作用下的应力分布规律,探讨了冻土地基特性(弹性模量、泊松比及地基系数)与温度的关系,对比了不同地基系数、冻胀量、管径、壁厚、温差以及上覆土厚度等特定条件下的管道应力峰值状况。计算结果表明:管道在过渡段与冻胀段及非冻胀段交界处有最大应力值,各类影响因素对管道交界处的应力影响最显著;地基系数的值越大,差异性冻胀量越大,管径越大,温差越大,管道交界处应力峰值也越大;管壁越厚,在管道交界处的应力峰值越小;管道上覆土层越厚,管道受冻胀作用弯曲应力越小,即加深上覆土层可降低管道由于冻胀抬升所产生的应力,可减缓管道变形。

When the buried pipelines crossing the permafrost regions suffering differential frost heave,the buckling deformation will occur,bringing potential safety problems to the pipelines. Thus,study on the influence of frost heaving on the pipes is an urgent affairs. In this paper,based on the theory of elastic foundation beam,a pipe-soil model subjected to frost heave is built. Stress distribution of a pipeline subjected to frost heave and other damages is revealed. The relationship between properties of permafrost foundation and temperature is also analyzed.The analyzed properties include elastic modulus,Poisson＇ s ratio and foundation coefficient. The stress peak distribution has simultaneously compared under various specific conditions,such as different foundation coefficients,frost-heave amount,pipe diameter and pipe wall thickness,temperature difference and overlyingsoil thickness. The results show that： 1） there is a maximum stress of pipeline in junctions between the transition zone and the frost-heaving zone or the non frost-heaving zone,and varied factors have obvious influences on the stress at the junctions of pipeline; 2） the greater the foundation coefficient value is,the greater the difference frost-heaving amount is; the larger the diameter,the bigger the temperature difference,and the greater maximumstress at the junction of pipeline; the thicker the pipe wall,the smaller the stress peak at the junction of pipeline; 3） the bending stress of pipeline caused by frost heaving will decrease with the increase of overlyingsoil thickness. It means that it will reduce the pipeline stress caused by frost heaving and restrict the pipeline deformation by deepening the overlying soil.