【作者】 肖军华；

【导师】 刘建坤；

【作者基本信息】 北京交通大学 ， 道路与铁道工程， 2008， 博士

【摘要】 列车循环荷载下路基表现出来的动力特性是引起线路运行条件恶化的主要原因。随着列车速度提高、轴重增加、运量加大,加剧了线路和列车的振动,增加了路基承受动荷载与振动频率的水平,提高了路基的振动加速度,加快了路基的累积变形和疲劳破坏。当前,对铁路既有线细粒土路基基床在提速列车动荷载与物理状态改变下的动态参数及规律研究较少,特别是对黄河冲积粉土这种特殊的路基填料在密实度变化与增湿条件下的应力-应变关系、强度特点、以及在列车循环荷载下的动态力学行为,甚至还没有过专门的研究。而现行的提速线路路基技术条件没有考虑列车荷载对路基的动力作用,使得列车长期运行对路基的影响难以定量计算,路基的评判与加固缺乏理论指导,给铁路运输带来安全隐患。本文在铁道部科技研究开发计划项目“京九线粉土路基病害整治技术试验研究(2005G012)”支持下,并结合铁路提速现状,以现场调查和实测为基础,以室内静、动力学试验为手段,通过理论分析和数值模拟,对提速列车荷载下粉土的力学响应与路基稳定性进行了研究,取得了以下几个方面的研究成果:(1)通过试验,掌握了黄河冲积粉土的土质特性,对非饱和粉土在密实度变化与增湿条件下的应力-应变关系、屈服特性、以及强度特点进行了对比研究;调查了黄河冲积粉土铁路路基的病害特点及现状。(2)通过试验,认识了粉土在列车循环荷载与土体物理状态改变下的变形与强度破坏演化机理,得到了影响粉土动态稳定性的主要控制性因素;研究了列车循环荷载下粉土累积塑性变形、回弹变形、回弹模量、临界动应力和动强度的变化规律,建立了上述力学参数与动应力和土体物理状态指标间的关系模型。(3)采用车轨耦合动力模型及现场实测数据,研究了提速列车动荷载的变化规律及数学模拟;通过ABAQUS建立轨道路基三维数值动力计算模型,对提速列车移动荷载下粉土路基的瞬态动力响应进行了分析,对比了列车轴重、速度、线路平顺性对路基动力响应的影响,并将计算结果与实测现象进行了比较;此外,还探讨了列车轴距、道床厚度、材料刚度、阻尼等参数对路基动力响应的影响规律,并借助正交设计原理,对各影响参数的显著性进行了评价。从机理上更深入了解了提速线路路基的动力特性。(4)通过分析当前国内外铁路组织和学者提出的不同的路基结构设计原则,结合既有路基的特点,探讨了采用基床动强度和路基累积变形作为提速下路基长期稳定的控制参数的合理性;在此基础上,以京九线粉土路基为对象,分析在不同运输条件、养护维修、道床厚度、路基容许变形下,路基结构要求的差异,并与现行技术条件进行了比较。更多还原

【Abstract】 The dynamic response of subgrade due to cyclic loading of moving train is the main reason of the deterioration of railroad.With increase in train speed,axle load and traffic weight of existing railway,the vibrations of train and track should be exacerbated, so the dynamic stress,loaded frequency,and vibration acceleration on subgrade will be grown,these should speed up the cumulative deformation and fatigue damage of subgrade.At present,there are very few studies on dynamic properties of fine-grained subgrade soils due to coupling effects of train loading increase and soil physical state changes.And there is even no special study on the deformation and strength characteristics of silt with varied compacting factor and water content,especially,the dynamic behaviors of silt under cyclic loading even has little literature.On the other hand,the effect of dynamic stress on subgrade is not be considered in the current subgrade specifications,which leads to difficult to predict the long-term effect of moving train on subgrade,in addition,there is also lack of a sound theoretical guidance system to evaluate and reinforce existing railroad subgrade,and these bring incipient faults for railway transportation.In this dissertation,silt railroad subgrade was taken as the study object,which has special characteristics and widespread distress as known.Field observations and testing results supplied the foundation to study,and according to laboratory static and cycling loading triaxial tests,theory analysis,and numeric simulation,the dynamic behaviors of silt and subgrade stability subjected to moving train loading were studied.Some achievements are as follows.(1)The properties of Yellow River alluviation silt were systemically studied. Especially,the changes of deformation and strength of this special soil with varied density and water moisture were obtained,at the same time,the subgrade distresses of railroad in Yellow River alluviation plain areas were also investigated and analyzed.(2)The dynamic deformation and strength mechanism of compacted silt with varied cyclic loading and soil physical states were apprehended,and the main controlled factors influencing the dynamic stability of compacted silt were obtained.The rules of cumulative deformation,resilient deformation,resilient modulus,threshold stress and dynamic strength of compacted silt were obtained,moreover,several prediction models about the relationships between these indices and stress and soil physical state were established.(3)The variations and expressions of wheel-track force with increasing train speed were studied by theoretical model of train-track and field observation data.After that, dynamic response of silt subgrade was simulated by tridimensional track-subgrade FEA model,and effects of axle load,train speed,and track smooth conditions were studied. During this course,the field observation results were applied to compare with calculated ones.Furthermore,effects of train axles distance,ballast thickness,material modulus and damping on subgrade dynamic response were also investigated,and significance tests of these parameters were carried out.(4)In order to consider the long-term effect of moving train loading on subgrade, two parameters,namely,dynamic strength and cumulative deformation of subgrade were selected as the controlled parameters of subgrade structure.Based on the two parameters and background of Jing-Jiu railroad,the required subgrade structures were calculated with different conditions of transportations,maintain periods,ballast thickness,and allowable settlement of subgrade,and comparisons between current specifications and the calculated subgrade structures were also done.更多还原