长寿柔性基层沥青路面的极限应变

长寿柔性路面设计通常采用沥青层底极限拉应变和土基顶部极限压应变作为控制指标。现阶段极限应变指标参照室内试验结果确定,且数值相对固定。而现场路面结构层应变响应值受结构厚度、荷载、环境作用（温度及老化）等因素的影响,在服役过程中不断演化。以2条服役超过35年的柔性路面结构（屯门公路与吐露港公路）为基础,分析了不同服役阶段路面结构层在不同荷载、环境作用下的极限应变响应,探讨了柔性路面极限应变的大概范围。研究结果表明：在初始服役状态下,屯门公路高温状态下沥青层底的极限拉应变为376×10^-6,土基顶部极限压应变为562×10^-6;低温状态下上述极限应变分别降为87×10^-6,249×10^-6;吐露港公路高温状态下沥青层底、土基顶部极限应变分别为149×10^-6,324×10^-6,低温状态下上述应变分别降为50×10^-6,156×10^-6。在经过长期服役后,老化状态下2类路面沥青层底拉应变及土基顶部压应变均大幅降低。屯门公路在使用36年后,某些路段出现零星的疲劳破坏,而吐露港公路则没有发现疲劳破坏。极限应变计算结果表明,路面关键位置的应变受荷载、沥青层厚度、温度和沥青层老化状态等多因素的影响。因此,在进行长寿柔性基层路面设计中,荷载、沥青层厚度、温度及沥青层老化状态等因素都应该考虑在内。

Endurance Strain Limits of Long-life Flexible Pavements

The design of long-life flexible pavements is often based on strain control, including controlling the horizontal tensile strain at the bottom of the asphalt layers and the vertical compressive strain at the top of subgrade soil. The current endurance limits of the strains were obtained under laboratory test conditions and have constant values. However, in situ strains at the critical locations are affected by the interactions between load configuration, load size, asphalt layer thickness, temperature, and asphalt aging status, exhibiting seasonal fluctuations and long-term trends. To obtain the approximate ranges of endurance strain limits, the mechanical responses of two heavy-duty traffic roads:the 35-year-old TuenMun Road and 36-year-old Tolo Road, were calculated. The results indicate that the maximum tensile strain at the bottom of the asphalt layer and compressive strain at the top of the subgrade soil for the newly constructed TuenMun Road at high temperatures are 376×10^-6 and 562×10^-6, respectively. At low temperatures, the strains decline to 87×10^-6 and 249×10^-6, respectively. For the Tolo Road, the maximum asphalt layer strain and subgrade soil strain at high temperature are 149×10^-6 and 324×10^-6, respectively. At low temperatures, these strains decline to 50×10^-6 and 156×10^-6, respectively. The strains corresponding to the asphalt layer and subgrade soil significantly decrease as the asphalt ages. On-site observations indicate that after 36 years of use, the TuenMun Road has developed sporadic fatigue damage, while the Tolo Road has no fatigue damage. Because the strains at the critical locations are affected by many factors, such as load configuration, load magnitude, asphalt layer thickness, temperature, and asphalt aging state, these factors should be considered in long-life flexible pavement design.