沥青路面中双层半刚性基层的倒装效应

Inversion Effect of Asphalt Pavement with Double Semi-rigid Base Courses

为探讨具有2层半刚性基层的沥青路面中半刚性基层的结构组合与材料选择原则,采用BISAR3.0对常用的具有2层半刚性基层的沥青路面结构及其基层倒装后的沥青路面结构进行了荷载效应分析;并成型了由2层不同半刚性材料构成的复合梁式试件,通过进行四点弯曲强度试验和四点弯曲疲劳试验对比了这两种结构的强度和疲劳寿命。结果表明:常用结构的下半刚性层所受拉应力、拉应变大于上半刚性层,路面结构的疲劳寿命取决于下基层;通常将性能稍差的材料用于下层,而性能较好的材料用于上层的结构组合原则与结构的水平应力状态不吻合;将其倒装后,性能较好的材料承受较大的拉应力,而性能较差的材料承受较小的拉应力,特别是当下层的模量大于上层模量的3倍时,上半刚性层会处于受压状态,这样就可以充分发挥各层材料的性能,且提高整个结构的抗裂性能;结构分析和试验均表明倒装结构的承载能力和抗疲劳性能均有显著提高;在进行半刚性基层的结构组合与材料设计时,应该根据结构层的水平拉应力状态进行结构组合与材料设计。

To study the structure combination and material selection principle for asphalt pavement with 2- layer semi-rigid base, the load effects in commonly used asphalt pavement structure with 2-layer semi-rigid base and its inverse structure are analyzed by using BISAR3.0 program. The composite beam specimens are molded with 2-layer different semi-rigid materials, and the strengths and fatigue lives of the 2 structure are compared through 4-point bending strength test and 4-point bending fatigue test. The result shows that （ 1 ） the lower semi-rigid layer of commonly used structure undertakes greater tensile stress and tensile strain than the upper semi-rigid layer does, and the fatigue life of the pavement structure depends on the life of the lower semi-rigid layer; （2） the ordinary pavement structural combination principle, i. e. , the material with poorer performance used for the lower layer and the better material used for upper layer, is not consistent with the horizontal stress state of the structure ; （3） after inversion, the better material will bear bigger tensile stress and the poorer material will bear less tensile stress, what is more, the upper semi-rigid layer will be in compress state when the modulus of lower layer is 3 times bigger than that of the upper layer. So, the inversed structure not only can make full use of the material of each layer, but also can significantly improve the crack resistance; （4） the structural combination and materials should be designed according to the structural layer＇ s horizontal tensile stress state in the design of structure combination and material for semirigid base.