接缝处弯沉对机场复合道面反射裂缝的影响

Influence of Joint Deflection on Reflective Crack in Airfield Composite Pavement

为研究机场复合道面PCC层接缝变形与反射裂缝的关系,采用ABAQUS有限元软件建立了复合道面三维有限元精细化模型,运用内聚力单元模拟了沥青层的损伤及开裂过程,提出了以退化因子及断裂面积率表征沥青层所受的整体损伤,开展正交试验分析了PCC层的板底脱空范围、接缝传荷系数、PCC层与沥青加铺层的层间摩擦系数及沥青加铺层厚度这4个因子对反射裂缝影响的显著性。基于显著性分析结果研究了板底脱空及接缝传荷系数与反射裂缝的内在联系,分析了弯沉、弯沉差与反射裂缝的相关关系。结果表明:仅受飞机荷载作用时,复合道面板底脱空对沥青加铺层反射裂缝有显著性影响,而通过改善层间黏结和增加沥青加铺层厚度对防治反射裂缝作用不大;沥青加铺层的反射裂缝与PCC层接缝处的弯沉和弯沉差紧密相关,采用弯沉差指标表征PCC层接缝变形对沥青加铺层反射裂缝的影响适应性更好;当PCC层存在板底脱空病害时,单侧脱空更易引起反射裂缝;良好的接缝传荷能力可有效减小接缝处的弯沉,延缓沥青加铺层的反射裂缝。因此,复合道面的防反设计应注意加强沥青层底部的抗开裂能力,建议采取措施恢复与提高接缝传荷系数,这对防治反射裂缝非常有效,尤其是对存在单侧脱空病害的情况。

To study the relationship between the joint deformation of PCC layer and reflective crack,a 3D FE model of the airfield composite pavement is developed.The damage and cracking process of the asphalt layer is simulated by cohesive unit.The degradation factor and fracture area rate are proposed to characterize the overall damage suffered by the asphalt layer.The significance of the influence of 4 factors(range of voids beneath slab of PCC layer,joint load transfer coefficient,interlayer friction coefficient between PCC layer and asphalt overlay,and thickness of asphalt overlay)on reflection cracks is analyzed by orthogonal experiment.Based on the result of significance analysis,the internal relationship between voids beneath the slab and joint load transfer coefficient with reflection cracks is studied,and the correlation among deflection,deflection difference and reflection cracks is analyzed.The result shows that(1)When only the airplane load is applied on the airfield composite pavement,the voids beneath the slab has significant influence on the reflective cracks of asphalt overlay,but improving the interface bonding and increasing the thickness of the asphalt overlay has little benefit on preventing the reflective cracks.(2)The reflection cracks of asphalt overlay are closely related to the deflection and deflection difference at the PCC layer joints.The adaptability is better when using deflection difference to represent the influence of joint deformation of PCC layer on the reflective cracks of asphalt overlay.(3)When there are voids beneath slab of PCC layer,the unilateral voids is more likely to cause reflective cracks.(4)Good joint load transfer ability can effectively reduce the deflection at the joint and delay the reflection cracks of the asphalt overlay.Therefore,the design of anti reflection for the composite pavement should pay attention to strengthening the anti cracking ability of the asphalt layer bottom.It is recommended to take measures to restore and improve the joint load transfer coefficient,which is very effective in preventing reflection cracks,especially in cases where there is void disease.