【作者】 陈士军；

【导师】 徐学燕； 凌贤长；

【作者基本信息】 哈尔滨工业大学 ， 岩土工程， 2013， 博士

【摘要】 目前，青藏铁路含融化夹层高温高含冰量多年冻土路基由列车荷载振动效应引起的沉陷问题日益显著，直接关系到客货列车的安全营运、青藏线能否提速等关键问题。同时，在全球气候暖化背景下，青藏铁路未受保温措施的低温基本稳定多年冻土路基必将进一步退化为高温不稳定多年冻土路基。鉴于此，本论文以青藏铁路低温高含冰量多年冻土路基在气候暖化和列车荷载共同作用下长期服役性能为应用背景，系统构建了一整套考虑热效应的大型高含冰量多年冻土路基振动响应三维模型。通过建立含相变路基温度场预测模型、精确求解轨－枕作用力实现路基响应模型的温度－应力耦合，并采用室内试验提供模型参数、现场监测实现模型验证等方法，探索青藏客货列车行驶下高温高含冰量多年冻土路基的振动响应规律。具体工作可总结如下：(1)基于附面层原理，并合理考虑施工期的影响，建立了多年冻土路基相变温度场预测模型。针对青藏铁路北麓河含厚层地下冰试验段地层结构、气候条件以及温升趋势，计算分析了路堤建成后未来50年路基地温分布走势。计算结果与监测数据吻合良好，验证了该温度场预测模型的正确性。(2)针对青藏铁路客、货列车编组形式及轨道结构特征，基于课题组研发的车辆－轨道动力耦合仿真程序ZL-TNTLM，并突破以往仅选取某一特定荷载时程或采用过于简化的荷载作为输入的局限，综合考虑轨道高低不平顺、谐波、动力型激扰和宽轨缝等不同激励因素的作用，从而获得了较符合实际的轨－枕作用力。并重点研究分析了车辆轴重、时速、以及各种激励因素下轨－枕作用力响应特性及影响规律。(3)基于低温动三轴试验，系统研究了列车移动荷载作用下冰的动力性能，建立了其在长期动载下永久变形预测模型，并给出主要影响因素及变化规律。计算的动力参数主要为多年冻土路基内厚层地下冰提供必要的参数。试验结果显示，可采用粘弹性模型来描述冰的动应力－应变关系。(4)基于上述工作，首次建立了以120个轨－枕作用力作为列车荷载输入并考虑热效应的大型三维路基振动响应模型。引入前述温度场预测结果，不仅与多点荷载输入共同作用于模型从而实现热－力耦合，还可体现多年冻土路基冻融过程。模型参数根据室内试验选取，采用等效线性化本构模型和无限元透射边界，基于显示动力分析方法开展数值计算，可初步得到青藏铁路多年冻土路基振动响应状态。结果表明该模型采用的多组轨－枕作用力多点动力输入可很好反映列车的移动特性。路基表层应力响应和青藏铁路列车行驶加速度反应现场监测结果进一步验证了模型的可靠性。(5)采用上述已验证的数值模型，计算得到了青藏客货列车以不同时速行驶并在不同激励因素作用时不同温度分布状态场地的振动响应。通过提取的竖向加速度和应力时程及其1/3倍频程谱分析，分别从时域、频域角度研究了轨道交通荷载作用下含融化夹层和厚层地下冰高温多年冻土路基场地效应，并分析了列车时速、激励因素和编组型式对路基振动响应的影响。同时，初步探讨了青藏列车行驶多年冻土路基应力路径响应特性，及其受路基深度、列车时速和温度状态的影响规律。本文研究成果有助于加深理解热效应下高含冰量低温基本稳定多年冻土普通道砟路基的退化过程及含融化夹层高温高含冰量多年冻土路基的振动响应规律。本文研究途径较为系统完备、成果真实可靠，可服务于青藏高原多年冻土区铁路建设。更多还原

【Abstract】 The Qinghai-Tibet Railway (QTR) is experiencing severe subgrade damagesresulting from train-induced vibrations, especially for some sections located in theice-rich warm permafrost site. The operation of passenger and freight trains and thespeed-increasing scheme of QTR may therefore be interrupted. Meanwhile thestablility of permafrost subgrage, without thermal-insulation-measures taken, willbe disturbed with the evolution of global warming. This will gradually lead to thegrowth of unstable warm permafrost. The present thesis attempts to evaluate thelong term operating performance of the ice-rich permafrost subgrade along the QTR,when subjected to traffic loads and annually increasing temperature. A completethree dimensional FEM model of the ice-rich permafrost subgrade is accordinglyestablished, taking thermal effect into account. Thermal-stress coupling isconsidered by simultaneously applying temperature field and the calculated track-sleeper force to the proposed model. The adopted research approach is becomingmore systematic with the implementation of laboratory tests and in situ monitoring.The original work is presented in detail as follows.1. Based on the boundary layer principle, a phase-based transient temperatureforecasting model of permafrost subgrade is built, with a proper consideration ofconstruction period. The temperature evolution of subgrade in the future50years uponthe completion of embankment construction is then predicted, considering the climateand geologic structure of the ice-rich Beiluhe section along the QTR. The numericalresults are in good agreement with the reference data.2. Considering the organization of passenger and freight trains and the trackstructure of the QTR, track-sleeper force induced by passing trains is more accuratelysimulated on the basis of the program ZL-TNTLM, taking also into account the verticaltrack irregularities, track gap and unstable vibration excitation. Special attention is paidto the effects of vehicle weight and running speed on the vibration loads.3. Cryo-dynamic triaxial tests of ice samples are conducted, with the aim to obtainthe required parameters for later research, as well as to carry out the correspondingdeformation-prediction and its influencing factors analysis. Ice could be well characterized by the visco-elasticity constitutive model according to the test results.4. Taking the well-calculated track-sleeper force as vibration input, a threedimensional track-subgrade coupling FEM model is initially built by using infiniteelement boundaries. Based on equivalent linear constitutive model, the obtainedtemperature field is simultaneously employed to the model to simulate thermal-stresscoupling effect, so that the freezing-thawing state of subgrade is available. Traffic loadsare shown to be well characterized by groups of multi-supported dynamic track-sleeperforces. The numerical model is further validated by the monitored acceleration anddynamic stress response at ground surface.5. Using the above well-validated numerical model, one can obtain the train-induced vibration response of the permafrost subgrade along the QTR. Based on thecomputed vertical acceleration and stress time histories, corresponding1/3octavebandwidth frequency response are also calculated. The vibration response of ice-richwarm permafrost subgrade induced by passing trains, and the effects led by differentfactors, are accordingly analyzed in both time domain and frenquency domain. Alsogiven interest is to the stress path of soil element subjected to traffic loading and itsinfluencing factors.The present thesis is aimed to provide preliminary sights into degradation tendencyof ice-rich permafrost subgrade with low temperature, and train-induced vibrationmechanism of warm permafrost subgrade with subsurface ice layer and unfrozeninterlayer. The proposed approach is complete, systematic and reliable, and is of interestin relation to the construction of permafrost subgrade along the QTR.更多还原