粗集料接触参数对沥青混合料损伤演化的影响

Influence of Contact Parameters of Coarse Aggregate on Damage Evolution of Asphalt Mixture

为了揭示沥青混合料内部细观损伤对宏观性能的影响,基于DIC方法与四点弯曲疲劳试验,对不同粗集料接触状态的混合料细观损伤尺度效应进行研究。首先以颗粒堆积理论与粒子干涉理论为基础,提出可表征细观主骨架结构状态的颗粒接触主力链配位参数(npfc)计算方法。采用SAC设计方法,通过控制关键筛孔2.36~4.75mm的分计筛余质量百分比,设计4组可反映不同粒径尺寸集料组合形式的SAC16级配(B60S00~B60S15),计算不同级配沥青混合料对应的npfc。其次,结合DIC方法与四点弯曲疲劳试验,分析疲劳荷载作用下沥青混合料小梁试件水平应变场演化特征,并提出混合料疲劳损伤因子定量分析方法。最后对不同粗集料接触参数的沥青混合料的细观损伤演化特征、疲劳损伤因子槇DFD及表征宏观抗疲劳性能的Km进行分析。研究结果表明:随着疲劳荷载作用次数的增加,4种不同npfc混合料的水平应变量逐渐增大,各槇DFD也均显著增加;随着npfc的增大,槇DFD明显减小,当npfc=7.73~9.55时,槇DFD较小,混合料的疲劳细观尺度损伤叠加效应较小;同时,随着npfc增加,Km呈先增大后略微减小的趋势;当npfc=7.73~9.55时,对应的宏观抗疲劳性能较好;因此,选取合理的npfc可优化沥青混合料内部主骨架细观结构状态,减少细观尺度损伤叠加效应影响,提高沥青混合料的宏观抗疲劳性能。

Research based on a digital image correlation method and four-point-bending fatigue tests was conducted to determine the relationship between meso-damage and macro-performance of asphalt mixtures.The different contact states of coarse aggregate were investigated to determine the scale effect of meso-damage of the asphalt mixtures.First,the three-dimensional packing and filling theory and the particle interference theory was used as a basis for proposing a computing method of the coordination number of particle contact force(npfc)and characterizing the stable state of the framework structure.By controlling the unit screening rate of the key screen mesh(2.36-4.75 mm)and using the SAC design method,four different SAC16 gradations,which reflect the combinations of the different particle size aggregates,were designed.Moreover,npfcwas calculated for asphalt mixtures with different aggregate gradations.Then,combining the digital image correlation method and the four-point-bending fatigue tests,the evolution of the horizontal strain field of asphalt mixture beam specimens was analyzed using the DIC method;aquantitative analysis method for fatigue damage factors of asphalt mixtures was proposed.Finally,the evolution of the meso-damage and the fatigue damage factor of asphalt mixtures were analyzed using the different contact parameters of coarse aggregate.Moreover,the analysis extended to the Kmvalue,which indicates the macro-fatigue resistance.The results show that with increasing fatigue loading,the horizontal strain distribution of the four different npfc asphalt mixtures changes from non-uniform to uniform,the strain variable increases from small to large,and the fatigue damage factors increases significantly.The fatigue damage factor decreases significantly with increasing npfc.When npfcis from 7.73 to 9.55,the fatigue meso-damage scale superposition effect of this graded asphalt mixture is small.Simultaneously,the Kmvalue,which characterizes the macroscopic fatigue resistance performance,tends to first increase and then decrease slightly as npfcincreases.When npfcis from 7.73 to 9.55,the corresponding macrofatigue resistance is better.Therefore,selecting a reasonable npfcoptimizes the meso-structural state of the main skeleton inside the asphalt mixture,reduces the effect of the meso-damage scale effect,and improves the macro-fatigue resistance of the asphalt mixture.