既有铁路开行大轴重列车路基的动力稳定性

Dynamic Stability of Existing Railway Subgrade under the Effect of Heavy Axle Load Trains

摘要:

为研究既有铁路开行大轴重列车路基的变形和强度稳定性，选取既有线典型路基土，借助动三轴仪，试验研究了重载下路基土的累积塑性应变和临界动应力，建立了路基土累积应变的预估公式；在此基础上，通过动力有限元分析得到了重载下路基的动应力，并基于分层总和法的思想计算了路基的动力附加变形. 研究表明，当路基压实系数低、饱和度高时，路基动力附加变形随列车轴重增加迅速增大，且轴重超过27 t，增大速率明显加快，但当路基压实系数大于一定条件，轴重增加对路基附加变形的影响较小；重载下路基动力附加变形的影响深度主要在2.5 m内，且显著影响深度约为1.0 m；重载下路基未发生动强度破坏情况下也会产生不能接受的永久变形. 可通过提高路基压实系数（或强度）显著减少重载下路基的附加变形量和变形达到稳定的时间.

关键词:既有线路基; 重载; 临界动应力; 动力附加变形

Abstract:

In order to study additional cumulative deformation and dynamic strength stability of railway subgrade under effect of heavy axle load train for existing railway lines, typical subgrade soil was selected to conduct cyclic triaxial tests to obtain the variations of cumulative plastic deformation and threshold stress under various physical states and cyclic loading conditions. Consequently, the prediction formula of cumulative strain was established. On this basis, by dynamic finite element method and layerwise summation method, dynamic stress and additional settlement of subgrade under heavy axle load were calculated. The conclusions are as follows: subgrade settlement rises rapidly with increasing in the axle load in conditions of low compaction or high saturation, and moreover, the settlement rises significantly when axle load exceeds 27t; but when the compaction coefficient is larger than a certain value, the increase of axle load has a smaller effect on subgrade settlement; the influential depth of additional settlement in subgrade under heavy axle load is mainly within 2.5m from subgrade surface, especially within 1.0m; under heavy axle load, subgrade may generate unacceptable permanent deformation even it meets the threshold stress condition. To reduce subgrade additional deformation and its duration under heavy axle load, the compaction coefficient or strength of subgrade should be improved.

Key words:existing railway subgrade; heavy axle load; threshold stress; additional dynamic settlement