【作者】 王立娜；

【导师】 凌贤长； 张世海；

【作者基本信息】 哈尔滨工业大学 ， 岩土工程， 2013， 博士

【摘要】 随着青藏铁路的通车，由列车荷载振动效应引起冻土路基的沉陷问题日益显著，直接关系到客货列车的安全营运、能否提速等关键科学问题。鉴于此，本论文以青藏铁路高温极不稳定多年冻土区路基在气候变化和列车荷载共同作用下的长期服役性能为应用背景，采用室内试验、理论分析和数值模拟相结合的技术手段，对青藏铁路列车荷载下冻土、融土的动力变形特性、列车荷载下路基振动反应和长期列车荷载作用下路基动力永久变形等科学问题进行了基础性研究，主要研究内容与取得的成果如下。(1)针对不同的动应力条件、环境温度和土体物理状态，通过低温动三轴试验，分析了冻结粉质粘土的动力变形特性，研究了列车荷载下冻土的弹性变形和累积塑性变形的变化规律，建立了冻土回弹模量的经验模型；并以临界动应力为归一化因子，进一步建立了冻土累积塑性应变与动应力条件、振动次数和冻结温度等参数之间的关系模型。(2)针对冻融循环与列车荷载作用特点，基于常温动三轴试验，研究了冻融循环次数、融化温度、动应力幅值等对融化粉质粘土的动态力学行为的影响，深入研究了冻融循环和列车循环荷载综合作用下融土的弹性变形和累积变形变化规律，并建立了回弹模量和累积塑性变形与冻融循环次数之间的关系模型，与以上建立的模型一并为后续计算分析青藏铁路路基永久变形提供依据。(3)针对青藏铁路路基的场地条件，采用有限元－无限元相结合手段，研究了列车行驶对多年冻土区路基三维振动反应的数值模拟途径。实现了温度场和应力场耦合，探讨了列车速度、轴重与路基的主要设计参数对路基振动反应的影响规律，并借助正交试验设计原理，对各影响参数的敏感性进行评价。(4)以建立的列车荷载下冻结、融化粉质粘土的累积永久应变模型为基础，二次开发了接口于粘弹塑性本构模型的CREEP子程序，建立了列车行驶路基累积永久变形预测模型。并基于该模型探讨了列车轴重、速度、等效振次和冻融状态等因素对路基累积永久变形发展的影响。更多还原

【Abstract】 With the completion of the Qinghai-Tibet Railway, several damages induced bythe traffic loads have been occurring to the permafrost subgrade, and the safe-operationdemand and speed-increasing scheme of the railway will therefore be affected seriously.In view of this, considering the background of the long term operating performance ofthe ice-rich permafrost sloped-subgrade along the QTR subjected to traffic loads andannually changing climate, the present thesis attempts to present relevant fundamentalresearches on such key issues as the dynamic performance of frozen and thawing soil,the vibration response of the subgrade, and the permanent deformation induced bytraffic loads. Laboratory tests, theoretical analysis and numerical simulation are takenas the main technological measures to perform the investigation. The original work ispresented in detail as follows.(1) Based on the Cyclic-dynamic triaxial tests, the dynamic behavior of frozen siltclay of the QTR subgrade subjected to the variation of dynamic stresses, of externalenvironmental conditions, and of physical features of soil is examined, and emphasis isalso given to the evolution of elastic deformation and cumulative plastic deformation offrozen silt clay induced by vibration loads. Specifically, a resilientmodulus-based-model is established on the basis of the obtained data, and the relationmodel between cumulative deformation and such parameters as dynamic stresses,number of vibration, and frozen temperatures is proposed as well, taking criticaldynamic stress as the normalization factor.(2) With the above-mentioned tests performed, a further research of the influenceof freezing-thawing cycles, thawing temperature, amplitude of dynamic stresses on themechanic features of the frozen silt clay of the QTR sloped-subgrade is carried out, inview of the characteristics of seasonally frozen soil and traffic loads. Special attention ispaid to the development of elastic and cumulative deformation of silt clay subjected toboth freezing-thawing cycles and traffic loads, and another relationship model ofresilient modulus, cumulative plastic deformation and freezing-thawing cycles isobtained, which together with the model mentioned above can provide theoreticalfoundation for the later calculation of permanent deformation of the QTR sloped-subgrade.(3) A three dimensional finite element-infinite element model on the vibrationresponse of the QTR sloped-subgrade is established. Our team’s train-track-subgradevibration program is adopted to simulate the traffic loads, that is, the calculatedtrack-sleeper forces, and the obtained forces are then imposed on the three-dimensionalsloped-subgrade model so that the temperature field can be coupled with the stress field.The effects of primary parameters such as travelling velocity, train axle, and subgradeon the vibration response of sloped-subgrade are compared based on the simulationresults, and the sensitivity analysis of parameters is performed trough intersectionexperiment design principle, by which the mechanism on the dynamic characteristics ofthe sloped-subgrade of warm permafrost region is further clarified.(4) On the basis of the established cumulative-permanent-strain model of frozenand thawed silt clay subjected to cyclic traffic loads, the Drucker-Prager-basedvisco-elastic plasticity sub-program CREEP is developed. Taking the well-obtaineddynamic stresses of subgrade as the initial state variable, the numerical model on thepermanent deformation of the QTR subgrade considering both the effects of groundpressures and dynamic stresses is built, based on which the permanent deformation ofsloped-subgrade induced by traffic loads is predicted, and the influence of train axle,traveling velocity, and vibration numbers on the permanent deformation is investigated.更多还原