青藏铁路路基粗颗粒填料动力特性和安定性行为研究

Study on dynamic properties and shakedown behaviors of coarse-grained fillers in Qinghai-Tibet Railway subgrade

对冻结路基填料开展一系列恒围压和动围压分级循环加载三轴试验,采用轴向及径向双向同步循环加载方式来模拟原位列车荷载下路基填料的复杂循环应力状态,试验结果表明:轴向累积塑性应变随冻结负温的升高而增大,随粗颗粒含量的增大而减小。体变随冻结负温的降低先减小再增大,而体变在粗颗粒含量增加下的三阶段演化特征被试验确定。最后采用现有的三类路基安定性评估理论对冻结路基填料的累积塑性变形进行评估,Werkmeister-准则和马-准则分别在动围压和恒围压的条件下易进入塑性蠕变阶段,陈-准则在两条件下的评判结果均属于塑性安定范围,后循环压实阶段与二次循环变形阶段间临界点不同的确定方法对安定性的评估结果有不可忽视的影响。

This paper presents a series of triaxial dynamic tests under constant and variable confining pressure to explore the characteristics of cumulative deformation and resillient deformation for frozen coarse-grained fillers.Testing results indicate that axial cumulative plastic strain increases with the increase of freezing negative temperature and with the decrease of the content of coarse particles. The volumetric strain first decreases and then increases with the decrease of temperature at five cyclic stress amplitudes. The three-stage development features of volumetric strain with the increasing of the content of coarse particles were experimentally determinated. The accumulative plastic strains of subgrade fillings were further analyzed and classified based on three existing shakedown criteria. The assessment capabilities of three shakedown criteria were examined by testing results. Based on Werkmeister criterion,the cumulative permanent strain of frozen sample has a tendency of arriving to the plastic creep area under variable confining pressure. According to Ma criterion,similar evaluation results can be found under constant confining pressure. The cumulative permanent strain of all testing samples distribute in the plastic shakedown area that corresponding to the Chen criterion. The defining method for demarcation point between the post-compaction compression stage and secondary cyclic compression stage is non-ignorable factor for reliably evaluating the cumulative plastic deformation of frozen coarse-grained fillers based on three criteria.