Analysis on fatigue cracking for asphalt surface layers based on field cores

Field cores from typical cracking locations were tested by the semi-circular bending test and the digital image correlation method to evaluate the anti-fatigue performance of different asphalt pavements. Test results were analyzed by different fatigue models. Causes of fatigue cracking for different pavement sections were determined by extraction and sieving test results. It is found that the ranking （from high to low） in terms of the anti-fatigue performance for field cores is the crumb rubber modified asphalt mixture, densegraded modified asphalt mixture, continuous graded asphalt treated base, gap-graded stone asphalt concrete, and half open-graded asphalt macadam. Compared with the half opengraded asphalt macadam, the fatigue life of the crumb rubber modified asphalt mixture improves by 2. 0 to 3. 8 times. Fatigue lives of different mixtures and distress ratios of actual pavements can be accurately predicted by the dissipated energy density ratio. Causes of fatigue cracking vary with mixture types.

接骨钢板断裂原因分析

通过宏观检验、化学成分分析和金相分析等方法对接骨钢板断裂原因进行了分析。结果表明,由于固定接骨钢板的螺钉强度过低,在使用中发生变形,造成固定孔松动,接骨钢板产生的横向弯曲应力超过疲劳断裂极限,发生早期疲劳断裂。通过改进螺钉制造方法,提高螺钉强度,可大大减少或避免接骨钢板的断裂。