Section II: structural composition characteristics of asphalt pavement (2) structural layer and performance requirements

1、 subgrade

subgrade Main indicators of performance ： Overall stability and deformation control .

2、 Cushion

Cushion Mainly set in Poor temperature and humidity conditions On the road , To improve the performance of pavement structure .
Cushion Main performance indicators of

• The cushion should be Sand 、 Gravel And other granular materials .
• Drainage bedding shall be connected to the edge drainage system , The thickness should be greater than 150mm, The width should not be less than the width of the base floor .

3、 The basic level

（1） The base course is a part of the pavement structure Bearing layer , It mainly bears the vertical force of vehicle load , And spread the stress transmitted from the surface course to the subgrade . And provide a stable and firm working face for surface construction , Control or reduce the adverse effects of uneven frost heave or settlement deformation of subgrade on the surface layer . The influence of natural factors on the base course is not as strong as that of the surface course , However, the base course under the surface course shall have sufficient water stability , To prevent large deformation after the base course is wet and soft , Cause damage to the surface course .
（2） Main performance indicators ：

• Should satisfy Structural strength 、 The ability to spread the load as well as Water stability and Frost resistance The requirements of .
• Impermeability . Asphalt seal coat or waterproof geotextile shall be laid on the top surface of subbase ; To prevent underground water seepage from affecting the subgrade , An impervious subbase composed of cement stabilized granular materials or dense granular materials shall be set under the drainage base .

4、 Surface course

（1） The surface layer is directly in contact with the air , Bearing traffic load Vertical force 、 Horizontal force and Impact force The role of , At the same time, it is affected by the erosion of precipitation and the change of temperature .
（2） Pavement service index ：

• Carrying capacity ： The pavement must meet the service needs of the design life , Have enough resistance to fatigue failure and plastic deformation , That is, it has quite high strength and stiffness .
• planeness .
• Temperature stability ： The pavement must maintain a high degree of stability , It has a lower temperature 、 Humidity sensitivity .
• Skid resistance .
• Noise quantity ： above （ Wearing course ） The layer adopts OGFC Asphalt mixture – Noise reduction and drainage .