多年冻土区铁路桥台-路基水热力耦合数值分析

Numerical Analysis of Hydrothermal Coupling Between Railway Abutment and Roadbed in Permafrost Regions

为研究多年冻土区铁路桥梁桥台冻胀倾斜病害的形成机理,并分析其变形规律,针对这一病害建立桥台-路基有限元模型,分析桥台后路基温度场特征及桥台冻胀倾斜规律。基于非饱和土渗流和热传导理论,联立冻土水热微分方程,并使用含冰量计算变形场从而实现水热力三场耦合。利用COMSOL软件建立三维桥台-路基水热力耦合模型,通过室内冻融试验验证该模型的有效性。最后以某多年冻土区铁路桥台为例,对桥台后路基未来30年间冻土上限、桥台冻胀倾斜展开研究分析。结果表明:在未来30年桥台后路基多年冻土上限呈现持续下降趋势,但桥台横截面冷空气的持续输入影响了路基不同位置处的冻土上限下降深度。在距离桥台4 m处路基多年冻土上限阳坡坡脚未来30年下降0.99 m、路基中心处下降0.92 m。在距桥台16 m处路基冻土上限阳坡坡脚未来30年下降1.6 m、路基中心下降1.81 m。在未来30年间,桥台后路基持续发生差异性水平冻胀,顶端累计水平位移155.6 mm、底端累计位移23.6 mm,桥台整体发生倾斜。

To study the formation mechanism of frost heave and tilt disease on railway bridge abutments in permafrost regions and analyze its deformation law,a finite element model of the bridge abutment subgrade is established to analyze the temperature field characteristics of the subgrade behind the bridge abutment and the frost heave and tilt law of the bridge abutment.Based on the theory of unsaturated soil seepage and heat conduction,the water and heat differential equations of frozen soil are established,and the deformation field is calculated using ice content to achieve the coupling of water and heat fields.By Using COMSOL software,a three-dimensional bridge abutment subgrade water thermal coupling model is developed and verified through indoor freeze-thaw tests.Finally,taking a railway bridge abutment in a permafrost area as an example,this study analyzes the upper limit of permafrost and the inclination of bridge abutment frost heave in the next 30 years for the roadbed behind the abutment.The results indicate that in the next 30 years,the upper limit of permafrost on the roadbed after the bridge abutment will continue to decrease,But the continuous input of cold air in the cross section of the bridge abutment has affected the depth of the upper limit of permafrost at various positions along the roadbed.At a distance of 4 m from the bridge abutment,the upper limit of permafrost on the sunny slope of the roadbed will decrease by 0.99 m in the next 30 years and that at the center of the roadbed will decrease by 0.92 m.At a distance of 16 m from the bridge abutment,the upper limit of permafrost on the sunny slope foot of the roadbed will decrease by 1.6 m in the next 30 years and that at the center of the roadbed will decrease by 1.81 m.In the next 30 years,the roadbed behind the bridge abutment will continue to experience a differential horizontal frost heave,with a cumulative horizontal displacement of 155.6 mm at the top and 23.6 mm at the bottom,resulting in an overall tilt of the bridge abutment.