【作者】 张锋；

【导师】 凌贤长； 冯德成；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2012， 博士

【摘要】 我国冻土面积分布广泛,冻融循环与重载汽车荷载是诱发季节冻土地区公路路基病害且由此引发路面破坏的两大主要原因。国内外关于季节冻土区重载汽车荷载下路基动力响应、长期重载汽车荷载下路基稳定性方面的研究罕有开展,公路路基病害机理认识不足。加之我国正处于高等级公路建设新时期,占国土面积超过一半的季节冻土地区内分布着纵横交错的国道、省道,如何有效评价季节冻土区(特别是深季节冻土区)高等级公路路基的稳定性与长期服役性能,有效降低路面、路基病害的发生且减轻运行维护难度,是制约我国寒区公路发展的瓶颈之一,也是我们面临的一大工程技术难题。鉴于此,本论文以深季节冻土地区高等级公路路基建造与运营维护为应用背景,采用室内试验、现场监测、理论分析、数值模拟相结合的技术手段,特别针对冻融循环与重载汽车荷载双重联合作用,开展重载汽车荷载下路基冻土与融土的动力参数、重载汽车-面层-基层-路基动力相互作用、重载汽车荷载下路基动力响应、长期重载汽车荷载下路基永久变形等科学问题研究,主要研究内容与取得的成果如下。(1)针对季节冻融循环与重载汽车荷载作用特点,基于低温动三轴试验研究了不同的含水量、冻融循环次数、荷载频率、负温、围压等条件下路基冻土动力参数;同时,基于常规动三轴试验研究了不同的含水量、冻融循环次数、荷载频率等条件下路基融土动力参数。以等效线性化模型描述冻土与融土的动应力～动应变关系,在经典双曲线模型基础上,提出了改进的Hardin双曲线模型以拟合冻土与融土的骨干曲线,分别研究了不同因素对最大剪切模量、最终剪应力幅值、最大阻尼比,以及剪应变幅值与剪切模量、阻尼比曲线的影响。(2)针对公路交通系统特点,在合理假设基础上,建立了深季节冻土区重载汽车-面层-基层-路基动力相互作用简化分析模型,包括典型重载汽车行驶振动简化分析模型、面层-基层-路基动力相互作用简化分析模型、春融期面层-基层-路基动力相互作用简化分析模型、正常期面层-基层-路基动力相互作用简化分析模型。以路面不平度作为重载汽车-面层-基层-路基系统的附加激励,轮胎点接触模型和改进弹性滚子模型作为轮胎与路面的接触关系,实现了重载汽车-面层-基层-路基的动力相互作用,并采用Wilson-θ逐步积分法求解动力体系方程。(3)在第(2)项理论基础上,开发了深季节冻土区重载汽车-面层-基层-路基动力相互作用简化计算程序DATPS,并采用前人试验结果和数值结果验证了计算程序的可靠性和理论模型的正确性。进而研究了重载汽车荷载下行车因素与道路因素对轮胎接地压力、路面动位移、基层顶面压应力的影响,并获取了基层顶面动压应力荷载时程。(4)针对深季节冻土区高等级公路典型路基,采用现场动应力监测手段,研究了三轴重载汽车在不同的整车质量、行驶速度时行车迹线下路基内动压应力传播规律和分布特性。采用有限单元法,基于虚功原理,将重载汽车-面层-基层-路基动力相互作用简化分析模型计算的基层顶面压应力时程作为荷载输入,建立了基层-路基-场地粘弹性动力有限元分析模型,并验证了数值模型的可靠性。进而分析了不同的汽车类型、后轴轴重、行车速度、路面不平度等级、路基融化厚度对正常期和春融期路基内动应力分布规律的影响。(5)基于常用长期循环荷载下土体永久应变模型,提出了冻融循环与重载汽车荷载联合作用下路基融土永久应变模型,根据三轴固结不排水压缩试验和长期重载汽车荷载下动三轴试验确定该模型参数。以应力比为关联,结合上述第(4)项研究成果,研究了不同的汽车类型、后轴轴重、行车速度和路基融化厚度对路基永久变形发展的影响,据此提出了深季节冻土区长期重载汽车荷载下路基永久变形预测公式。更多还原

【Abstract】 The frozen soil are widely distributed in China, freeze-thaw cycle and heavy truck load are main causes of subgrade diseases causing pavement destroyed in these regions. However, there are few researches on the dynamic responses of pavement and subgrade induced by heavy truck and stability evaluation of long-term heavy truck load in seasonally frozen soil regions at home and abroad. Additonnaly, our country is in the new periods of highway constructions and many of them are distributed in seasonally frozen regions (especially in deep seasonally frozen regions), so the effective evaluation of long-term performance and stability of subgrade in these regions and the control of subgrade and pavement diseases are the bottlenecks of highway development and the technical problems faced by scientific workers.Therefore, employing laboratory test, field monitoring, theoretical analysis and numerical simulation, especially according to the coupling effect of seasonal freeze-thaw action and heavy truck load, this paper investigated dynamic parameters of the frozen and thaw soil induced by heavy truck load, dynamic interaction of heavy truck-surface course-base course-subgrade, dynamic responses of subgrade induced by heavy truck load, and permanent deformation of subgrade induced by long-term heavy truck load. The main contents and results are as fellows.(1) According to the features of freeze-thaw cycles and heavy truck load, adopting the low temperature dynamic triaxial test, the paper investigated the effects of water content, numbers of freeze-thaw cycle, loading frequency, negative temperature and confining pressure on dynamic parameters of the frozen soil. Meanwhile, the effects of water content, numbers of freeze-thaw cycle, and loading frequency on dynamic parameters of the thawed soil by employing the normal triaxial test were studied. In the paper, the relationships between dynamic stress and strain were described by equivalent linearization model, the backbone curves of the frozen and thaw soil were fitted by improved Hardin Hyperbolic Model, and the effects on the maximum shear modulus, maximum damping ratio, the relationships between shear strain and shear modulus and damping ratio were studied.(2) According to the characteristics of highway traffic system, the dynamic interaction simplified analysis models of heavy truck-surface course-base course-subgrade in seasonally frozen regions based on some reasonable hypothesis were developed, which included typical heavy truck model in highway, surface course-base course-subgrade dynamic model, surface course-base course-subgrade dynamic model in spring thawing and normal periods. The dynamic interaction of heavy truck model and surface course-base course-subgrade model was realized by taking surface roughness as systematic excitation and taking tire point contact model and improved elastic roller model as contact. Finally, dynamic equations of system were solved using Wilson-θmethod.(3) Based on the theory of the second term, the program DATPS was developed for investigating the dynamic interaction of heavy truck- surface course-base course-subgrade in deep seasonally frozen regions, and the validation of the model and reliability of program were verified by the test and simulated results. The effects of driving factors and road factors on tire ground pressure and pavement dynamic displacement were investigated by program DATPS, and the time histories of dynamic compressive stress time histories of top base were obtained.(4) The propagation law and distribution characteristic of dynamic compressive stress of the subgrade soil induced by the three axles heavy truck with different speed and weight were studied by field monitoring. Based on principle of virtual work, taking the dynamic compressive stress time history caculated by simplified model of the dynamic interaction of heavy truck-surface course-base course-subgrade model as the input of load, viscoelastic dynamic finite element models of base course-subgrade-ground verified by the field monitoring data were built. Then the effects of traffic type, rear axle load, running speed, highway grade and thawing depth on distribution law of subgrade dynamic stress during normal and spring thawing periods were analyzed by numerical simulation method.(5) Consided the freeze-thaw cycle and heavy truck load, the permanent strain model were established and the model parameters obtained by the consolidated undrained triaxial test and dynamic triaxial test under cyclic load. Refered to stress ratio as a link and based on the fourth term, the effect of traffic type, rear axles load, running speed and subgrade thickness on the permanent deformation induced by long-term heavy truck load were investigated by the numerical method. Hereby, the prediction formula of subgrade permanent deformation induced by long-term heavy truck load was established.更多还原