排水沥青混合料单轴静态蠕变试验的离散元仿真

Discrete Element Simulation of Uniaxial Static Creep Test of Porous Asphalt Mixture

为揭示排水沥青混合料单轴静态蠕变试验的细观力学机制,综合室内试验和数值模拟相结合的方法,采用图像识别技术获取车辙板粗集料及孔隙细观信息,并基于离散元建立单轴静态蠕变试验模型,围绕沥青模量、粘结强度和混合料孔隙率等3个因素对排水沥青混合料高温性能的影响开展了研究。结果表明:在相同的外荷载作用时间下,模量对永久变形的降幅影响略大于蠕变柔量,模量由1倍提升至5倍,蠕变柔量约降低3.7倍,永久变形降低约4.7倍;模量增大至4倍后,永久变形量和蠕变柔量的降幅趋于平缓;空隙率由18%提升至22%,蠕变柔量和永久变形量均增大约40%,混合料耐久性明显降低,空隙率18%-19%阶段对永久变形和蠕变柔量的增幅较为平缓,19%-22%阶段永久变形和蠕变柔量的增幅增大,且接近线性关系;混合料承载力随粘结强度提高而增大,不同粘结强度(280、300、500 N)对永久变形量和蠕变柔量的影响基本一致,且低粘结强度(250～300 N)对永久变形量和蠕变柔量的影响远大于高粘结强度(300～700 N)。在影响蠕变柔量与永久变形计算值可靠度的3个因素中,按可靠度高低排序依次为:粘结强度、空隙率、模量。

In order to reveal the meso-mechanics mechanism of uniaxial static creep test of porous asphalt mixture,image recognition technology was used to obtain the coarse aggregate and the pore mesoscopic information of rutting slab,through combining laboratory test and numerical simulation.Based on the discrete element,a uniaxial static creep test model was set up and the influence of three factors such as asphalt modulus,bond strength and mixture porosity on the high temperature performance of asphalt mixture was studied.The results show that,under the same external load and acting time,the modulus has a slightly greater effect on the decrease of permanent deformation than creep compliance.The modulus increases from 1 to 5 times,the creep compliance decreases by 3.7 times and the permanent deformation decreases by about 4.7 times.When modulus increases to 4 times,the decrease amplitude of permanent deformation and creep compliance tends to be gentle.The porosity increases from 18% to 22%,and creep compliance and permanent deformation increase by about 40%.The durability of the mixture is obviously reduced.The increase of permanent deformation and creep compliance is gentle in the stage of porosity ranging from 18% to 19%;the amplification of permanent deformation and creep compliance increases and approaches linear relationship in the stage of porosity ranging from 19% to 22%.The bearing capacity of the mixture increases with the increase of bond strength.The effect of different bond strengths(280,300,500 N)on the permanent deformation and creep compliance is basically the same,and the effect of low bond strength(250-300 N)on the permanent deformation and creep compliance is much greater than that of high bond strength(300-700 N).Among the three factors affecting the reliability of creep compliance and permanent deformation,bond strength,porosity and modulus are in turn.