高速铁路路基沉降与列车运行速度关联性的研究

土质路基在高速列车的长期循环荷载下不可避免会发生沉降变形,列车运行速度与路基的沉降有着直接的关联性。随着列车运行速度的不断提高,对不均匀沉降变形的控制要求也越来越严格;同时,路基的不均匀沉降也制约着列车运行速度的提升,故有必要研究无砟轨道路基不均匀沉降对列车运行特性和线路冲击的影响。在既有的列车-轨道垂向耦合动力学理论模型基础上进一步考虑了轨道板下方的CA砂浆层和混凝土垫层的共同作用,建立了更符合实际线路特征的车轨耦合分析模型,并通过与现场测试结果的对比验证了该模型的合理性。基于此模型考察了不同路基沉降分布特征、不同列车运行速度条件下车辆和轨道振动特性,从车辆运行安全性和乘客舒适性两方面的指标总结了沉降的控制要求。计算发现短波长的路基沉降易于引起轮轴较大的加速度响应,线路的沉降幅值控制标准主要由安全性指标(轮轴减载率)决定;而在发生大波长的路基沉降时,主要导致车体加速度响应明显增大,路基沉降控制标准主要由列车车体舒适性指标(车体加速度)所决定,并给出具体的控制参数。     

轨枕空吊对有砟道床动力特性影响的离散元分析

为研究轨枕空吊对有砟道床动力特性的影响,建立有砟轨道的离散元分析模型。通过缩小与枕底相接触的道砟颗粒的粒径实现了轨枕空吊的模拟,研究了轨枕空吊状态下有砟道床的动力响应,分析了轨枕空吊形式和空吊数量对有砟道床动力响应的影响。结果表明:轨枕空吊会使得道床中道砟颗粒接触力发生重分布,空吊轨枕所在道砟箱中强力键的个数会减少,两侧相邻道砟箱中强力键的个数会增多,轨枕非完全空吊时在列车荷载作用下会对道床产生冲击作用而增大部分道砟颗粒受力;空吊轨枕会失去对其下方道砟颗粒的约束作用而导致道砟颗粒振动的离散性增加,同时会增大轨枕盒中道砟颗粒的振动并显著提高两侧相邻轨枕下方道砟颗粒的振动水平;轨枕空吊会增大轨枕侧面与道砟颗粒之间的摩擦耗能,引起道砟出现"泛白"现象,同时还会增大两侧相邻轨枕下方道砟颗粒之间的摩擦耗能;3根轨枕连续完全空吊对道床动力响应的影响大于1根轨枕完全空吊的影响。     

路基不均匀沉降对地铁A型车辆动力学特性影响研究

路基不均匀沉降会导致轨道变形,进而映射到钢轨造成轨面不平顺,对行车安全和运行平稳性带来影响。针对城市轨道交通整体道床典型轨道结构,基于车辆-轨道耦合动力学理论,建立考虑轨道自重荷载和轮轨接触关系的车辆-整体道床无砟轨道空间耦合动力学实体模型,分析了路基不均匀沉降条件下车辆行驶速度、路基不均匀沉降波长和幅值等参数对车辆动力学特性的影响。分析结果表明:随着车辆行驶速度和路基沉降幅值的增大,车辆系统动力学响应也响应增大,当速度超过85 km/h时对行车安全性和舒适性均造成不利影响,且路基不均匀沉降引起车辆动力学响应的敏感幅值为30 mm;路基沉降波长对车辆动力学特性的影响呈先增大后减小的变化规律,其中在波长为20～30 m时对车辆动力学特性影响最为显著。     

基于车辆响应的无砟轨道路基不均匀沉降评价指标理论研究

路基不均匀沉降的合理评价对于保障高速铁路运营安全和指导线路养护维修至关重要。传统路基沉降评价多基于沉降幅值单一指标,缺乏对车辆运营速度、路基沉降波长的综合考虑。该文基于建立的精细化多车-无砟轨道-路基耦合动力学模型,分析了路基不均匀沉降下的车辆动力学响应特征以及运营速度、沉降波长及幅值对车辆响应的影响规律,在此基础上提出了沉降时变率指标用于路基不均匀沉降评价。结果表明:沉降时变率能融合车辆运营速度、沉降波长、波幅三者对高速列车动力学响应的共同影响。沉降二阶时变率和轮轨垂向力、轮重减载率安全性指标呈显著的线性映射关系;沉降一阶时变率和车体加速度等舒适性指标呈较为显著的线性映射关系;并提出了轮重减载率、车体加速度与沉降时变率的拟合公式。研究成果可为高铁线路设计和养护维修提供参考。     

重载铁路路基足尺模型试验研究

以朔黄重载铁路为工程背景,通过构建重载列车模拟加载系统和路基足尺模型,开展路基动力响应试验,分析了在循环加载条件下路基的动力响应特性。试验结果表明,路基中不同深度动应力峰值均随着轴重的增加而增加,轴重越大,动应力的影响深度越大,路基中动应力随深度的增加呈负指数衰减趋势。路肩处动位移峰值随轴重的增加而线性增加。当轴重增加到30 t后,路基达到临界破坏状态,可见按照原朔黄铁路路基建造标准,其最大运行列车轴重约为27 t,如再增加列车轴重,路基需预先采取强化措施。试验结果对建造运行列车模拟加载系统及足尺路基模型具有借鉴参考意义,同时有助于深刻理解列车轴重对路基动力响应特性的影响。     

地面沉降对路基上双块式无砟轨道平顺性的影响

高速铁路无砟轨道对于基础沉降变形特别敏感,地面沉降会显著影响路基上无砟轨道的受力变形及使用寿命,影响高速列车安全平稳运行。该文针对路基上双块式无砟轨道,基于有限元方法建立了梁-板-实体空间耦合模型,对地面不均匀沉降的幅值、范围及型式与双块式无砟轨道系统平顺性的关系开展了研究。结果表明:无砟轨道及路基各层沉降量随着地面沉降量增加基本成线性增加,支承层和路基表层间沉降差较大易出现离缝问题;地面沉降量20mm、沉降范围小于15m时,路基及轨道结构离缝现象明显,沉降范围大于15m时结构变形趋于平缓、轨面曲率半径增大;地面错台和折角型不均匀沉降均易导致无砟轨道及路基在折角点出现沉降差、结构离缝甚至开裂,折角值大小直接影响轨面平顺性。     

胡家屯中桥路桥过渡段动力特性试验研究

通过对秦沈铁路客运专线胡家屯中桥路桥过渡段进行动力响应现场测试和沉降观测,分析了级配碎石路桥过渡段的沉降规律;动应力、振动加速度、动位移与列车速度的关系,以及动力响应沿路基深度的衰减规律和沿线路纵向变化规律。结果表明:级配碎石过渡段能减缓路桥间沉降差;随着列车速度的提高,列车对路基的动应力作用增强,且动应力影响在基床表层较为显著;不同行车速度下,各测点振动加速度值变化不大,其分布范围一般集中在1 m/s2～3.5m/s2之间;各测点动位移受列车速度的影响不明显,其值集中在0.1 mm～0.35 mm范围内变化。     

基于高速铁路路基冻胀的轮轨动力响应研究

季节性冻土区高速铁路无砟轨道路基冻胀,影响了列车运行的安全性、舒适性以及无砟轨道主体结构的服役性能。为研究路基冻胀和高速行车荷载组合效应下的轮轨动力响应,建立了车辆-轨道-路基冻胀耦合动力学模型,对路基不同冻胀幅值、冻胀位置和行车速度下CRTSⅠ型板式无砟轨道轮轨动力响应及轨道结构受力进行分析。结果表明:冻胀发生区段轮轨动力响应增大,列车以350 km/h运行时的安全性和舒适性满足冻胀管理标准要求,但轮轨力随冻胀幅值和速度的增加而增大;轨道板和底座板振动加剧,在计算冻胀波长和幅值范围内,离缝处轨道板振动加速度峰值超过动态验收标准要求,容易引起离缝处CA砂浆层及路基基床表层伤损破坏,且轨道板、底座板振动加速度随行车速度增加而增大;轨道结构动应力和列车荷载传递关系密切,路基冻胀状态下列车荷载引起轨道板和底座板处于交替和交变的拉压受力状态,需要在设计中提出控制裂纹的措施,行车速度对短波冻胀时轨道结构受力影响较小。     

武广高速铁路无砟轨道路基动力响应试验研究

在武广高速铁路典型路基断面埋设测试元件,分别于“联调联试”阶段和运营2年后进行了动车组列车荷载作用下的路基动力试验,实测了路基动应力、振动加速度、振动速度等动力响应。分析了路基动力响应与列车速度的关系、动力响应沿路基深度变化规律和路基动力特性在运营前后的变化情况。结果表明：基床表层顶面轨下位置动应力响应比中线处大;动态响应在基床表层范围内最为强烈且衰减较快;列车荷载速度对动应力幅值影响较小,对振动加速度幅值影响较大。运营2年后与“联调联试”阶段相比,基床表层顶面动应力幅值、振动速度幅值相差不大,而振动加速度幅值在“联调联试”阶段较大;两次试验测得的z=2.7m时(基床底层底面)路基动应力幅值和振动加速度幅值的衰减率依次为73.40%~79.30%和79.28%~86.90%,z=4.2m时（路基本体内）两者衰减率依次为82.99%~89.06%和92.78%~96.31%;而振动速度幅值,z=1.8m时（基床底层内）衰减率范围为75.62%~80.80%。     

连续梁桥边墩不均匀沉降下轨道层间变形协调关系及动力学应用

高速铁路连续梁桥边墩沉降将造成其上简支与连续梁桥的共同变形,边墩不均匀沉降差引起的轨道几何形位改变直接影响列车运行平稳性和安全性。该文基于APDL建立考虑引桥与路基及其上轨道结构影响的高速铁路CRTS II型无砟轨道-变截面连续梁桥系统精细化仿真模型,通过大量的仿真计算,探明了边墩不均匀沉降差与轨道几何形位改变的轨道层间变形协调机理。基于线性回归方法获得了不同连续梁桥跨度条件下,边墩不均匀沉降差与轨道几何形位改变的层间变形协调关系的定量函数表达式,进而采用该仿真模型、文献模型及列车-轨道-桥梁耦合动力学理论验证其拟合精度和正确性。最后基于定量函数表达式研究了边墩不均匀沉降差对列车运行平稳性和安全性的影响。结果表明:三种模型计算结果吻合良好,说明该文定量函数表达式具有较高精度;在边墩不均匀沉降工况下,存在激振频率接近车体自振频率的临界跨度,发生共振时,显著恶化列车运行平稳性;采用大跨度连续梁桥可有效降低边墩不均匀沉降差、提升乘坐舒适度、降低轮轨力及缓和列车与轨道动态作用效应;沉降差小于25 mm时,轮重减载率随跨度的增大而显著减小。     

Effects of maintenance operations on railway track's mechanical behaviour by field load testing

Deterioration of track causes variations in different mechanical parameters such as value and distribution of track vertical stiffness, which would change the way track mechanical components behave in service condition or maintenance operations. As a result, studying deterioration effects and that of maintenance operations such as tamping and dynamic stabilisation on the mechanical behaviour of both standard and deteriorated tracks could give a better picture of track condition and effectiveness of maintenance operations. In this paper, by carrying out static and dynamic tests and using 89 measurement sensors, the influence of mechanised maintenance operations on mechanical behaviours (strain, acceleration and displacement of rail and sleeper) of a high-deteriorated track and a low-deteriorated track is investigated. The tests were carried out in three different stages (before tamping, after tamping and after track dynamic stabilisation) under a passing train (a 6-axle locomotive and a 4-axle wagon) with 20-ton axle load. Observations indicate that track deterioration causes non-uniform track stiffness and load distribution along the track, such that rail heel strain time history under train loading changes from maximum tensional pattern under the wheels to maximum compressive pattern between two wheels of a bogie. Tamping and dynamic stabilisation cause a more uniform load distribution, which reduces strain and increases acceleration in rail and sleeper. Effects of these maintenance operations on sleepers are far more than that of rail. Deteriorated track is stiffer than low-deteriorated track; stiffness distribution is less uniform and its rails are subjected to less strain and acceleration.     

Prediction of displacement induced by tilting trains running on ballasted tracks through measurement of track impact factors

In the track design and behavior prediction, the variable contribution of wheel load was evaluated by considering the design load for the tracks. Further, the track impact factor was used to calculate the dynamic wheel load as a single value, which was chosen according to the rail type (i.e., continuous welded rail or joint rail) and the design speed but did not take into consideration the track conditions (i.e., the ballast condition good or bad), train type (i.e., tilting train and EMU), and track components (i.e., sleeper type and fastening type). In this study, the measured track impact factor was applied to the time history function of the FE analysis in order to predict the displacement of ballasted tracks under real conditions, which included curved and the deteriorated tracks, thus increasing the train speed by approximately 20–30% of the existing train speed. Therefore, the dynamic wheel load and the rail and sleeper displacement were measured for two different trains running on four conventional curved track sections with two different sleeper types. The track impact factor was estimated from the measured dynamic wheel load, and the empirical dynamic wheel load was calculated using the measured track impact factor at each site. The measured track impact factors were used for simulating the dynamic wheel loads applied on the derived time history function for fast trains. A finite element analysis model using the derived time history function based on the empirical dynamic wheel load was used to predict the train-induced track displacement. The numerical simulations and field test results were compared with German and Japanese regulations for train-induced track displacement, and the speedup effect of a tilting train was compared with that of a general train (EMU).The empirical track impact factors were 17–18% higher in the R400 sections than in the R600 sections. As the track curvature decreased, the impact on the track increased. Therefore, the empirical track impact factors were 21–23% higher in the WT sections than in the PCT sections. At 70 km/h, the impact on the track from a tilting train was 7–11% less than that from EMU. Although the tilting train sped up by 30% (90 km/h), its response level was similar to or less than that of the EMU. The analytical results reproduced the experimental results well within about 2–5% difference in the values. Therefore, the derived time history function based on the measured track impact factors is considered to provide sufficiently reliable FEA results in the investigation of the behavior of ballasted tracks. The difference between the maximum displacements for both train types on all the sections was about 15–20%.The analytical results show that the speed limits of the tilting train were higher than those of the EMU by approximately 8–23 km/h at each test site. Therefore, the speed limit of each test site was estimated by considering the limit of sleeper displacement. It was shown that the time history function derived using the measured track impact factor on a small track curvature with wooden sleepers was higher than that in other test sections. Therefore, it would be advantageous to increase the weight of sleepers on existing lines to increase the train speed through the speedup effect without increasing the track curvature. The increase in the speed of a tilting train with a small track curvature was much better than that by a track curvature increased by approximately 10%.     

高速列车荷载作用下无砟轨道地基竖向耦合动力响应研究

建立高速列车荷载作用下车辆系统-无砟轨道-地基耦合动力模型,通过Fourier变换求解弹性半空间地基土体的动力控制方程,同时根据轨道底座与半空间的接触条件得到了弹性半空间表面竖向位移在频域内的表达式,再采用快速Fourier 变换求得了时域内的土体位移解。结合算例,分析了列车速度、轨道结构参数等因素对地基动力响应的影响。研究结果表明:板下调整层弹簧刚度系数越大,地基土动力响应越大,地表振动越大;底座弯曲刚度越大,地基土动力响应越小;随着列车速度增加,地基土动力响应增大;距离轨道中心处越远,地基土动力响应越小。     

有砟梯式轨枕轨道减振性能的理论分析与试验研究

为实验室铺设有砟、无砟两种梯式轨枕轨道,用自由落锤激励装置对两种梯轨减振性能进行对比研究。建立有砟梯轨、有砟普通轨道的数值模型,利用试验测试结果对模型进行验证。通过在模型中施加货运列车荷载对比两种有砟轨道减振性能。结果表明,有砟梯轨减振性能不及浮置式梯轨,在低频段有一定减振能力,20 Hz以下振动经道砟平均衰减25 dB,对控制重载货运列车环境振动具备潜在优势;梯式轨枕对分散列车冲击振动、降低时域内峰值有明显优势。     

轴荷载作用下铁路交通地面振动的半解析法研究

根据波数域内分层地基波动方程的求解理论，推导铁路有砟轨道、无砟轨道与地基的耦合振动方程，得到了波数域内的统一表达形式。材料阻尼采用粘滞阻尼。利用Fourier变换，在频率。波数域内求解振动微分方程，再通过Fourier逆变换得到大地表面的振动响应。分析了轨道和地基之间的能量传递特征，简谐荷载对振动衰减的影响，并对列车轴荷载引起的地面振动进行了仿真分析。结果表明：铁路有砟轨道和无砟轨道与地基之间的动力作用有较大差别；在简谐荷载作用下，地面振动的衰减曲线出现波动；本文方法具有较大的计算域，可以模拟编组较长的列车通过时引起的地面振动。