一年内列车荷载作用下冻土路基的应力分布

冻土路基土体的物理性质与温度有密切关系, 在不同的季节, 路基内的变形场和应力场会相应发生变化. 为了说明路基内变形场和应力场的季节性差异, 以青藏铁路某断面为例, 对冻土路基在有、无列车荷载两种工况下进行了数值模拟, 系统分析了两种工况下路基内的变形场和应力场特点. 结果表明: 路基修筑后, 在自重作用下会产生较大瞬时变形; 由于路基内温度场随时间变化, 路基内各点的位移也随时间发生变化, 且位移时程曲线与温度时程曲线大体呈负相关. 在有、无列车两种工况下路基竖向位移分布都是由道砟中心向路基内部逐渐减小, 但数值明显不同; 由列车荷载引起的最大竖向附加变形发生在路基顶面中心点, 在10月15日、1月15日、4月15日, 变形量分别为-4.94 mm、-3.24 mm、-2.56 mm. 对于路基底面中心点和地基浅层中心点, 由列车荷载引起的附加应力在10月15日最大、1月15日次之、4月15日最小, 附加应力最大达到19.48 kPa; 列车荷载主要影响路基上部土体应力分布, 对下部土体应力分布影响较小.

Research on the stress distribution within embankment on permafrost under train load in a year

The physical properties of frozen soil in the embankment are impacted by environmental temperature. So, the deformation field and stress field of embankment will change seasonally. In this paper, the deformation field and stress field of a typical section of Qinghai-Tibet Railway in cold region are simulated and analyzed. Two conditions are considered namely with train passing and without train passing. The following conclusions can be drawn: 1) After the embankment construction, instantaneous deformation will occur under the gravity of soil. The deformation will change with time. The change tendency of the time-history of deformation is nearly negatively correlated with that of the time-history of temperature; 2) The vertical displacement of embankment will gradually decrease along the direction from the surface to the inner part of the embankment, no matter there is train passing or not. The maximum vertical additional deformation takes place at the center point of the embankment top. The additional deformation values are -4.94 mm, -3.24 mm, -2.56 mm, respectively, on Oct. 15, Jan. 15 and Apr. 15. For the center points at the embankment bottom and shallow layer of ground foundation, the additional stress is largest at Oct. 15 and smallest at Apr. 15. The maximum additional stress can reach 19.48 kPa. The influence of train load on the stress distribution in the upper part of embankment is larger than that in the lower part.