SBS改性沥青混合料疲劳极限拉应变研究

Determination of Fatigue Ultimate Tension Strain of SBS Modified Asphalt Mixtures

为了证实和确定SBS改性沥青混合料疲劳极限标准,通过控制应变的小梁疲劳试验,研究了SBS改性沥青混合料疲劳寿命随拉应变水平的变化规律,拉应变水平的变化模拟了实际路面沥青层厚度变化对层底拉应变的影响.结果表明:当拉应变水平较高时,沥青混合料疲劳寿命有限;随着拉应变水平降低,疲劳寿命逐渐增大,且拉应变水平越低,增幅越大;当拉应变水平由400×10-6向100×10-6变化时,疲劳曲线在200×10-6处有明显的转折,此后,随着拉应变水平进一步降低,疲劳曲线明显变得平缓,呈现典型的渐近线特征,这证实了SBS改性沥青混合料存在疲劳极限这一假设;基于交通发展、设计年限和经济性,通过理论计算,建议SBS改性沥青混合料疲劳极限拉应变可以采用140×10-6.

The purpose of this study was to investigate and verify the theoretical fatigue limit for SBS modified asphalt mixtures.To investigate this,the flexural beam fatigue test was used to test an asphalt mixture under different tensile strain levels.Varying the tensile strain levels allowed the simulation of a range of pavement thicknesses,from thin pavements（high tensile strain levels） to thick pavements（low tensile strain levels）.The results show that there is a finite fatigue life for the asphalt mixtures under higher tensile strain levels.As the tensile strain level decreases,fatigue life of asphalt mixtures increases.The lower the level of tensile strain,the greater the increasing rate of fatigue life for evaluated asphalt mixtures.When the tensile strain level changes from 400×10^（-6） to 100×10^（-6）,the fatigue life curve has a clear turning point at 200×10^（-6）.As the strain level reduces further,the fatigue life curve becomes flat obviously and exhibits a typical feature of asymptote.The trend indicates that asphalt mixture had a fatigue limit.When the tensile strain level is less than the limit tensile strain level,the asphalt mixture should have a tendency of infinite life.Based upon the traffic development,period designed and economy, there is a fatigue ultimate tensile strain around 140×10^（-6） for the evaluated mixture.