青藏铁路填土路基热-力耦合离散元研究

Study on thermal-mechanical coupling of the Qinghai-Tibet Railway embankment based on discrete element method

多年冻土是含有冰的特殊土体,在自然环境变化及工程扰动下易发生冻胀融沉变形,严重威胁着青藏高原工程建筑物的安全稳定,特别对青藏铁路的畅通运营提出了严峻挑战。以青藏铁路五道梁地区路基断面为研究对象,采用颗粒离散单元法,通过建立热-力离散元计算模型,对路基的温度场和变形进行了计算和预测。结果表明:离散单元法克服了有限元方法无法模拟颗粒间导热与接触粘结作用的瓶颈,能够从微观层面阐释宏观变化,较为真实地反映冻土的导热和力学变形;离散单元法数值计算分析发现,随着运营时间的增加,路基存在冻土退化问题,而且路基中颗粒间热交换复杂,在0℃等温线区域和路基坡脚处,颗粒间相互作用更为突出。热-力耦合离散元为冻土工程研究提供了新思路,可更好地为寒区工程服务。

Permafrost is a special soil that contains ice.The frost heave and thaw settlement of permafrost always occur under natural environment change and engineering disturbance,which threat the stability of the construction in the Qinghai-Tibet Plateau and affect the normal transportation of the Qinghai-Tibet Railway particularly.An embankment in Wudaoliang area is used as an example.Based on the simulated thermal-mechanical model of discrete element method,the temperature and deformation variation of the embankment are calculated.The results show that,compared with the finite element method,the discrete element method can not only simulate the heat transfer and bond action between particles,describe the macroscopic change by explaining the micro level,but also can reflect the heat-mechanics state of frozen soils;with additional time,the degradation of permafrost embankment will occur.In addition,the heat transfer between roadbed particles is complex,especially in 0℃isotherm area and the slope toe of embankment.This study can provide new ideas for the research of permafrost engineering and better serve engineering in cold regions.