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为了研究沥青疲劳特性在常应力模式下的演变规律,采用动态剪切流变仪(Dynamic Shear Rheometer,DSR),在应力控制模式下对70#基质沥青和SBS改性沥青进行时间扫描试验,获得复数剪切模量(G*)、耗散能变化率(DR)和累计耗散能比(DER)3种物理指标随荷载作用次数的变化曲线,通过分析3种曲线变化规律确定沥青疲劳寿命:(1)G*值下降到初始值50%时对应的荷载作用次数(NG*);(2)DR-N曲线转折点对应的加载次数(NDR);(3)DER-N曲线转折点(70#基质沥青)和曲线偏离DER=N直线20%时(SBS改性沥青)对应的加载次数(NDER),并建立沥青疲劳破坏方程。结果表明:NG*处于复数剪切模量加速下降阶段,而NDR和NDER处于沥青缓慢破坏和加速破坏转折阶段,NG*是根据经验所确定,而NDR和NDER是根据曲线转折点定义,物理意义明确;70#基质沥青和SBS改性沥青疲劳寿命(NG*、NDR和NDER)与应力在双对数坐标中表现出良好的线性关系;70#基质沥青疲劳破坏规律性强,疲劳曲线有明显的转折点,能明确定义沥青疲劳寿命;而改性沥青由于改性剂的作用,沥青弹性恢复能力增强,沥青疲劳曲线变化规律不明显;相同分析方法下,SBS改性沥青疲劳寿命明显优于70#基质沥青;随着加载应力提高,两种沥青的疲劳寿命均下降。
In order to study the evolution of asphalt fatigue characteristics in normal stress mode, the dynamic shear rheometer (DSR) was used to time-scan the 70 # matrix asphalt and SBS modified asphalt under stress control mode to obtain The fatigue life of asphalt is determined by analyzing the variation curves of three kinds of physical indexes, such as complex shear modulus (G *), dissipation energy dissipation rate (DR) and cumulative dissipation energy ratio (DER) (2) the number of loadings (NDR) corresponding to the turning point of the DR-N curve; (3) the turning point of the DER-N curve (70) # Asphalt) and the corresponding loading times (NDER) when the curve deviates 20% of DER = N straight line (SBS modified asphalt), and the asphalt fatigue failure equation is established. The results show that NG * is in the stage of accelerating decline of complex shear modulus, while NDR and NDER are in the turning stage of slow asphalt and accelerated destruction. NG * is determined empirically. NDR and NDER are defined according to the turning point of the curve and the physical meaning is clear ; 70 # matrix asphalt and SBS modified asphalt fatigue life (NG *, NDR and NDER) and stress in the double logarithmic coordinates showed a good linear relationship; 70 # matrix asphalt fatigue damage regularity, fatigue curve obvious Turning points, can clearly define the fatigue life of asphalt; and modified asphalt due to the role of modifiers, asphalt resilience enhancement, asphalt fatigue curve changes are not obvious; the same analysis method, the fatigue life of SBS modified asphalt was significantly better than the 70 # Base asphalt; With the increase of loading stress, the fatigue life of the two kinds of asphalt all decreased.