【作者】 平树江；

【导师】 申爱琴；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2009， 博士

【摘要】 截止2008年底,我国高速公路总里程达到6.03万公里,而已建高速公路中,90%以上为半刚性基层沥青路面,这类路面结构优势明显,承载力高、水稳性和耐久性好,但是半刚性基层开裂普遍,易使路面出现反射裂缝,进而引发路面结构性破坏是这类路面的致命缺点。纵观我国近20年来沥青路面结构设计及使用状况,设计控制指标与路面破坏形式不一致、路面结构单一状况严重影响了沥青路面的使用寿命。鉴于此,本研究引入了耐久性沥青路面设计理念,以寿命周期内总费用最经济为原则,力求整个路面结构在设计使用年限内,不发生结构性破坏,仅需定期的功能性养护。在此基础上,最终提出适合我国气候、交通、材料、经济等状况的耐久性沥青路面设计指标及结构设计方法,以提高我国沥青路面的设计使用品质。本文首先针对沥青路面结构性破坏类型,分析了国内外高等级沥青路面基层的使用状况,系统研究了耐久性沥青路面常用基层的适应性,重点对复合式基层的适应性进行了深入分析,认为复合基层可有效改善半刚性基层的开裂和反射裂缝,相比而言,更适合作为耐久性沥青路面的基层。建立了有限元模型,计算分析了层间结合状态对复合式基层沥青路面结构内部力学响应的影响,特别就沥青路面层间不同接触状态及路面结构参数对路面剪应力的影响规律进行了深入研究。利用“路面层间材料多功能剪切仪”,试验研究了不同温度条件下各类路面层间材料的抗剪切性能,推荐了透层、封层及粘层材料的适用类型及最佳用量。根据层间材料剪切破坏过程的损伤机理及破坏状态的变化,定义了剪切破坏的三阶段,认为整个剪切破坏过程中,材料之间的粘结力、机械咬合力及摩擦力逐步产生作用。研究提出了与沥青路面结构性破坏对应的复合基层耐久性沥青路面设计指标体系。认为可以拉应变控制沥青层的受力状态,以层底拉应力控制半刚性基层的受力状态,以路基顶面压应变控制路基塑性变形,建议基顶压应变的设计值为200με,以路表弯沉为设计和竣工验收指标,使设计与质量控制指标相对应。为控制面层局部损坏和层间剪切破坏,建议对沥青混合料内部最大剪应力和面层、基层间最大剪应力进行验算,特别应重点分析路表l0cm深度内结构层的剪应力,并对之进行抗剪强度验算。合理确定沥青混合料的疲劳极限是耐久性沥青路面设计的基础,但该值的确定目前国内外尚无统一标准。本文在分析常规应变条件下沥青混合料疲劳破坏发展的基础上,改进了ASSHOT T321中所推荐的疲劳寿命计算方法,根据混合料劲度模量的变化规律,将疲劳破坏过程分为三个阶段,以第二阶段的试验数据推算低应变条件下试件的疲劳寿命,并利用UTM疲劳试验机,通过小梁重复弯曲疲劳试验测试了不同低应变水平下沥青混合料的疲劳性能,得出了山东滨州耐久性路面ATB-25和AC-25的疲劳极限为70με-80με。在低应变状态下,沥青混合料的疲劳寿命和应变水平仍能很好地符合幂函数疲劳方程,可根据常规应变水平下的沥青混合料疲劳寿命推断出低应变状态下的疲劳寿命。在计算分析的基础上,提出了耐久性沥青路面的结构设计原则。根据半刚性基层的破坏模式和受力特点,将其分为上部抗裂功能层和下部抗疲劳功能层,并提出了两个层次的合理厚度。对于抗裂功能层,可选择骨架空隙结构和骨架密实结构以及减少混合料中结合料的用量,有效控制开裂的发生；对于抗疲劳功能层,可选择骨架密实结构以及采用较高的结合料用量,提高结构层的疲劳寿命。通过大量的理论分析及实验研究,确定了复合式基层耐久性沥青路面结构,并铺筑了试验路。通过试验路定点实测反算各结构层模量值,并进行力学反算,发现铺筑的复合式基层耐久性沥青路面应力、应变值均满足耐久性沥青路面设计要求,且较其他结构偏于安全。寿命周期费用分析结果表明,在40年～50年的设计寿命内,复合式基层耐久性路面经济效益非常可观。更多还原

【Abstract】 By the end of 2008, China’s total expressway mileage has reached 60,300 kilometers. More than 90% of these expressways were built with semi-rigid asphalt pavement structure. Such kind of pavement structure has obvious advantage in structure with high bearing capacity, better water stability and lasting quality, but its fatal drawback is that semi-rigid base is universally easy to crack and easy to make some road reflective cracking, leading to structural damage (early cracking and reflection cracks caused by temperature and drying shrinkage of semi-rigid base material are apt to lead to cracks up through all the structure). Through reviewing nearly 20 years of asphalt pavement structural design and its application in our country, it can be seen that the inconsistent control index of design with the road damages and the single pattern of pavement structure have seriously affected road performance and life expectancy. In view of this, following the principle of the most economical life-cycle cost, the design concept of durable asphalt pavement is introduced in this paper in order that no structural damages occur in the entire design life or just a regular fuctional maintenance are needed. On this basis, control index and structural design methods of durable asphalt pavement suitable for China’s climate, transportation, materials, economy and other conditions are proposed to improve the quality of design and service of our asphalt pavements.In this paper, regarding asphalt pavement structural damage, application of high-grade asphalt pavement at home and abroad was analyzed and adaptability of durable asphalt pavement especially with composite base was systematically studies. So it is considered that composite base can effectively prevent semi-rigid base from cracking and reflection cracks. Comparatively speaking, it is more suitable to be used as the base of durable asphalt pavement.A finite element model was set up and impact of the interlayer bonding state on the internal mechanical response of asphalt pavement with composite base was analyzed. Particularly different contact states between layers and impact of pavement structure index on shear stress were deeply investigated. With "multifunction shear apparatus for pavement interlayer materials", shear resistence of different types of pavement layer materials under different temperature conditions was tested and analyzed and suitable materials and optimum dosage for prime layer, sealing layer and adhesive layer were recommended. According to the damage mechanism and its changing pattern in the shear failure process of interlayer material, shear failure was defined into three stages and it is believed that adhesive force between materials, machinery bite force and friction gradually act in the whole process(of shear failure).In the research, a road design index system of durable asphalt pavement with composite base corresponding to asphalt pavement structural damage has been proposed. The tension strain is taken (as the design index) to control the strained condition of the asphalt layer while the tension stress in the bottom layer (as the design index) to control the strained condition of semi-rigid base and the compressive strain on the top of the subgrade is to control the subgrade plastic deformation and the design value of compressive strain on the top of the subgrade is recommended as 200με. The road deflection is to be taken as the index (target) of design and completion in order to make the design corresponding to the quality control. It is recommended that maximum shear stress in the asphalt mixture and between surface layer and base layer should be recomputed in order to control local damage in the surface layer and shear damage between layers, especially analysis should be focused on the shear stress of the structure layer in 10cm depth and its shear strength should be checked.It is the base for the design of durable asphalt pavement to determine a reasonable fatigue limit of the asphalt mixture, but there is no uniform standard for the determination of the value either at home or abroad. Based on the analysis of fatigue damage of asphalt mixture under normal strain condition, computing methods for fatigue limit recommended by ASSHOT T321 was modified. According to the variation trend of mixture stiffness modulus, the fatigue failure process is divided into three stages. Test data of the second stage are proposed to be used to calculate the fatigue life of the specimen under low strain condition. Trabecular repeated bending fatigue tests were conducted with UTM fatigue testing machine to test fatigue performance of asphalt mixture at different strain conditions and ascertain that fatigue limit of durable pavement ATM-25 and AC-25 is 70μεto 80μεin Bin Zhou, Shandong province. The fatigue tests also show that the fatigue life and strain level of asphalt mixture can still keep consistent well with power function fatigue equation even under low strain condition. So, the fatigue life of asphalt mixture under low strain condition can be inferred by its fatigue life under normal strain condition.Based on computation and analysis, structural design principles for durable asphalt pavement were proposed here. According to the destruction model and load-bearing characteristics of semi-rigid base, it is divided into upper anti-cracking function layer and lower anti-fatigue function layer with reasonable thicknesses for both layers. For anti-cracking function layer, it is recommended to choose skeleton void structure and skeleton dense structure as well as to reduce the amount of binder in the mixture to effectively control the occurrence of cracking. For anti-fatigue function layer, skeleton dense structure and higher amount of binder are to be selected to improve the fatigue life of structure layer.Through enormous amount of theoretical analysis and experimental studies, structure of durable asphalt pavement with composite base was confirmed and a trial road section was built. By in-situ tests on the trial road section, modulus values of all structure layers were inverted and the pavement structrue was calculated. It was found that stress and strain values of the durable asphalt pavement with composite base can meet the design requirements and it is safer than other structures. As analysis of life-cycle cost show, in 40 to 50 years of design period, great economic benifit of durable asphalt pavement with composite base can be expected.更多还原