多孔沥青混合料堵塞规律离散元仿真

Discrete element simulation of porous asphalt mixture clogging law

为揭示多孔沥青混合料孔隙堵塞机理,开展了多孔沥青混合料堵塞模型试验与仿真模拟结合研究;基于电子计算机断层扫描与离散元软件PFC3D V5.0分析了多孔沥青混合料孔隙特征,得到了多孔沥青混合料的孔隙数据;在PFC3D V5.0中投放各粒径集料并根据孔隙特征生成压实虚拟试件,以MATLAB切片对比实际试件孔隙图像验证模型准确性;在自重条件下设置特定级配组成堵塞物侵入多孔沥青混合料试件模拟仿真,并以室内试验结果对照验证,改变投放堵塞物粒径,分析了试件孔隙衰变率,找出了堵塞敏感颗粒;在自重条件下引入流体模拟仿真试验,改变了流体渗流速度,分析了试件堵塞变化规律。研究结果表明:PFC3D V5.0生成的虚拟试件具备较高的精确度,仿真揭示了试件堵塞规律,小颗粒除堆积于喉孔处产生堵塞外,还会在嵌挤成型后与大粒径颗粒积聚产生堵塞;自重条件下的堵塞主要集中在混合料试件上层30 mm处,相应堵塞敏感颗粒粒径分布为0.150~0.600 mm,堵塞颗粒粒径分布对堵塞结果影响较大;在重力与流体条件下,随着渗流速度从0.005 m·s^(-1)增加到0.030 m·s^(-1),孔隙衰变率变化速度增加,残留在混合料内部的堵塞物减少,孔隙衰变率减小,排水沥青路面在设计与养护时也需将当地降雨条件带入考虑。

To reveal the pore clogging law of porous asphalt mixture,the combination study of model experiment and simulation of porous asphalt mixture clogging was conducted.The pore characteristics of the porous asphalt mixture were analyzed based on the CT-scanning and discrete element software PFC3D V5.0,and the pore data of the porous asphalt mixture were obtained.The aggregates of different particle sizes were put into PFC3D V5.0,and the compacted virtual specimens were generated according to the pore characteristics.The accuracy of the model was verified by comparing the pore images of actual specimens with the MATLAB slices.In the self-weight condition,the simulation was set with the porous asphalt mixture specimen being intruded by clogging particles with specific gradation composition.The data of indoor experiments were compared and verified.The particle sizes of clogging particles were changed,and the pore decay rates of the specimen were analyzed.The clogging-sensitive particles were identified.In the self-weight condition,the fluid simulation experiment was introduced,and the change law of specimen clogging was analyzed by changing the seepage rate of fluid.Analysis results show that the virtual specimen generated by PFC3D V5.0 has high accuracy,and the simulation reveals the clogging law of the specimen.The small particles not only accumulate at the throat position causing clogging,but also congregate and interlock with the particles of larger sizes resulting in clogging too.In the self-weight condition,the clogging is mainly concentrated at the upper 30 mm of the mixture specimen,and the size distribution of corresponding clogging-sensitive particles is 0.150-0.600 mm.The size distribution of clogging particles has a great impact on the clogging results.In the conditions of gravity and fluid,with the seepage rate increasing from 0.005 m·s~(-1) to 0.030 m·s~(-1),the changing rate of pore decay rate increases.In addition,the clogging particles remaining in the mixture decrease,accompanied by the reduction of the pore decay rate.Therefore,the local rainfall conditions should also be considered in the design and maintenance of drainage asphalt pavement.2 tabs,20 figs,30 refs.