【作者】 李长雨；

【导师】 刘寒冰；

【作者基本信息】 吉林大学 ， 道路与铁道工程， 2012， 博士

【摘要】 随着国家经济的快速发展，道路交通的作用愈来愈凸显其重要性，其对国民经济的影响力也越来越大。我国季节性冻土分布广泛，其区域遍及长江以北10余省市，占全国总面积的53.5%，季节性冻土区的道路损害多由冻胀和翻浆引起，路基的冻胀和翻浆造成了其力学性能指标的降低。提高季节性冻土区路基的稳定性、增强抗冻融特性，降低冻害现象，对保证季冻区道路的长期安全运营具有重要应用价值。本文针对季节冻土地区的道路冻害问题，依托国家高技术研究发展计划（863计划）项目《季节冻土区路基抗冻融稳定控制技术研究》，以国道G102线扩建为工程依托，开展了冻融循环下橡胶颗粒改良粉煤灰土的理论与应用研究，本文的研究工作体现在以下几方面：1.在已有的研究结果基础上，对橡胶颗粒改良粉煤灰土的静力特性进行了研究，通过无侧限抗压强度试验、抗冻性试验以及保温性试验，提出了2%橡胶颗粒含量的粉煤灰土（1：2）混合料作为季节性冻土区路基冷阻层材料，室内试验证明了橡胶颗粒改良粉煤灰土抗压强度高、冻胀量小和保温性好的特性。2.运用动三轴试验手段对橡胶颗粒改良粉煤灰土与纯粉煤灰土的动力参数进行了对比研究，分析了在不同围压下两种材料的动强度、动模量的变化规律，得出在一围压下，橡胶颗粒改良粉煤灰土和粉煤灰土的动强度与破坏周数成反比，破坏周数相同，动强度与围压成正比，橡胶颗粒改良粉煤灰土的初始切线模量低于粉煤灰土的初始切线模量，平均动模量大于未改良前的结论。3.利用课题组研制的路基材料力学参数测试试验机，开展了橡胶颗粒改良粉煤灰土混合料的冻融试验研究，在动荷载作用下，分析了材料在冻融过程中力学特性的演化过程，得出了混合料的力学指标随正负温度变化规律，以及与冻融循环次数的关系。通过监测材料内部温度的变化，得出了在外环境温度变化下混合料内温与应力、应变的演化过程。对监测的应力、应变数据分析，得出了动应力随着温度的下降而随之降低，当温度在正负方向进行转变时，动应力有一个突然减小的变化。冻融循环前四次的动应力略有下降，但下降的幅值较小，冻融循环5～8的动应力趋于稳定。动应变随着温度的降低而下降，动应变在前四次冻融循环时的应变值随着冻融循环次数的增加逐渐减小，但从第五次冻融循环开始动应变变化较小，趋于稳定。每次循环的动模量始终维持在一个比较稳定的值附近；当温度减小到一定程度时，动模量将不再发生改变；相同冻融循环，不同温度下，橡胶颗粒改良粉煤灰土的动模量随着温度的增加而增加，但增加值很小；相同温度，不同冻融循环下，橡胶颗粒改良粉煤灰土的动模量经过3～8次冻融循环动模量变化稳定。4.为了进一步验证橡胶颗粒改良后粉煤灰土的路用性能，探索其在季节冻土区道路建设中推广应用，以国道G102线提高公路等级的工程为依托，在G102线上建立1公里实验路。铺设三种不同路基填料的试验路段，在道路中心处，三种路基填料层的上、下表面分别埋设了温度传感器，在不同温度时期监测了三种路基填料上、下表面的温度数据，分析得出橡胶颗粒改良后的粉煤灰土具有热传导性低，保温性能好的特性。5.采有限元热分析理论，对冬季时期粉煤灰土、橡胶颗粒改良粉煤灰土及粉质粘土三种材料的路基温度场进行了有限元分析，建立了带有冷阻层的路基三维有限元模型，监测了三种路基填料的最大冻深、温度梯度等冻结参数，分析得出采用橡胶颗粒改良粉煤灰土的冷阻层底面温度最高，冷阻层的道路冻深最小，其温度梯度最大，采用粉质粘土冷阻层的道路冻深最大，温度梯度最小。同时分析确定了采用橡胶颗粒改良粉煤灰土的最小填筑厚度，此厚度确保在该路基填料下方的路基处于正温状态。更多还原

【Abstract】 With the fast development of economy, the role of road transport is more and moreimportant and its influence on the national economy is growing. Seasonal frozen soil inChina is widely distributed throughout more than10provinces in the north of the YangtzeRiver, taking up53.5%of the country’s total area. Road damage in seasonal frozen soil areais mostly caused by frost heave and frost boiling, which reduce the mechanical propertyindex of seasonal frozen soil. Improving the stability of roadbed in seasonal frozen soil areaand enhancing its freezing-thawing resisting characteristics as well as reducing freezinginjury are of great value to ensure the long-term safety operations of road in seasonal frozenarea.In this paper, freezing issues in seasonal frozen soil area are discussed based on theNational High Technology Research and Development Program (863Program)-“Technologycontrol study on roadbed resisting freezing-thawing stability”, relying on G102nationalhighway expansion engineering projects. Meanwhile, the theory and application research onrubber particles modified fly ash soil under freeze-thaw cycles is carried out in this paper,with the main research work below:The rubber particles modified fly ash soil static properties are studied based on theexisted research results. By unconfined compressive strength tests, the frost resistance testand insulation test, we proposed fly ash soil mixtures (1:2) with2%rubber particles as coldresistance materials for roadbed in seasonal frozen soil areas. Laboratory tests proved thatrubber particles modified fly ash soil has properties of high compressive strength, smallamount of frost heave and good insulation.1. By using dynamic three axis test, and through the comparison of the dynamicparameters between rubber particles modified fly ash soil and pure fly ash soil, and theanalysis of the change law of these two materials’ dynamic strength as well as dynamicmodulus under different confining pressures, we concluded that under the same confiningpressure, the dynamic strength of rubber particles modified fly ash soil and pure fly ash soilis inversely proportional to the damage circle number, while under the same damage circlenumber, the dynamic strength is proportional to the confining pressure, with the initialtangent modulus of rubber particles modified fly ash soil lower than pure fly ash soil as well as the average dynamic modulus larger than the unmodified fly ash soil.2. By using roadbed material mechanical parameters testing machine developed byResearch Group, we carried out the freezing-thawing tests of rubber particles modified flyash soil mixture. Under dynamic loading, we analyze the evolutionary process of themechanical properties in the process of freezing and thawing, and obtained the variation lawof mechanical index with positive and negative temperature as well as its relationship withFreezing and thawing cycles. By monitoring the temperature change inside the material, wecame to the evolutionary process between Mixture temperature and stress and strain whenthe outside temperature was changing.3. By analyzing the monitored stress data and strain data, we concluded that dynamicstress reduced with the decrease of temperature, and at the time of temperature changingbetween the positive and negative direction, there was a sudden decrease change for thedynamic stress. The first four dynamic stresses of freezing-thawing cycles decreased slightlybut the amplitude was small. And after5~8freezing-thawing cycles, the dynamic stresstended to be stable. Dynamic strain fell as the temperature decreased. The first four strainvalue decreased with freezing-thawing cycles increasing. But since the fifthfreezing-thawing cycle, the dynamic strain changed a little and tended to be stable. Dynamicmodulus of every circle was always maintained in a stable value. When the temperature wasreduced to a certain extent, dynamic modulus would no longer change. With the samefreezing-thawing cycle but different temperature, the dynamic modulus of rubber particlesmodified fly ash soil increased with the temperature increasing but the added value wassmall. When the temperature was the same but the freezing-thawing cycles was different, thedynamic modulus of rubber particles modified fly ash soil tended to be stable after3~8times.4. In order to further verify the road performance of fly ash soil improved by rubberparticles and explor the popularization and application of road construction in seasonalfrozen soil, we establish an1000m long experimental path on national highway G102line.We pave three different subgrade test sections and bury temperature sensor in thecenter,the top and bottom of the road at three roadbed filler layer. Then we collect thetemperature data of the roadbed filler at different location in different temperatureperiod.Analysis result shows that the rubber particles improved fly ash soil has low thermalconductivity and good thermal insulation performance.5. On the basis of FEM thermal analysis theory, subgrade temperature field of fly ash soil, the rubber particles modified fly ash soil and silty clay is studied.An subgradedimensional finite element model with insulating layer is established.Using this model,wemonitor parameters of subgrade frozen deep, the temperature gradient freeze of threeroadbed filler.Then we obtain the conclusion as follows: the temperature of the bottom ofinsulating layer is the highest on rubber particles improved fly ash soil.The insulating layerhas the minimum road freeze depth and the maximum temperature gradient; Silty clay acrossthe stratosphere has the maximum to freeze depth and the minimum temperature gradient. Atthe same time, we determine the minimum filling thickness of the rubber particles improvedfly ash soil. This minimum filling thickness can insure the roadbed is under a state ofpositive temperature.更多还原