摘要
沥青混合料的宏观性能与组分相材料性能和内部结构特征等密不可分,因此从微细观角度研究沥青混合料宏观性能是十分必要的。考虑微细观结构特征及其演变的力学试验的数值模拟,它将组分材料性能和宏观性能定量地结合起来,进而把握沥青混合料不同力学特性之间的平衡,并避免了大量的室内经验性试验。
本文首先采用CT技术和DIP技术研究两种成型条件下三种级配沥青混合料试件的内部空隙特征,并采用数学模型对其进行表征。结果表明,沥青混合料的空隙空间分布规律受试件成型方法及级配类型的影响较大。不同级配条件下,马歇尔试件内部空隙分布沿着高度方向总体呈现对称形状,而静压试件内部空隙分布则为“一端大,一端小”的形状;相同级配条件下,静压试件的平均空隙率和平均空隙数量均较大,但平均空隙等效直径相差较小;采用两参数数学模型能够表征沥青混合料内部空隙空间分布规律,以及成型方法和集料级配对其的影响。
再则,基于黏弹性理论,利用CT技术、DIP技术和FEM方法对沥青混合料二维数值模型进行虚拟间接拉伸试验和虚拟蠕变试验研究,通过分析两种试验条件下均质模型与非均质模型内部结构力学响应,提出虚拟蠕变试验最佳试验面的选取方法,并分析了劈裂荷载作用下混合料损伤开裂位置及原因。结果表明,与均质模型相比,非均质模型可以更准确地模拟蠕变实验;沿试件高度方向选择不同的试验截面不会对数值试验结果产生影响,因此沿此方向的任意截面均可作为虚拟蠕变试验的最佳试验面。非均质模型与均质模型的间接拉伸试验的应力S11与S22曲线变化趋势均相同;均质模型最大压应力位于模型中心,非均质模型最大拉应力位于砂浆与粗集料的界面处,且竖向路径的最大拉应力大于横向路径的最大拉应力,据此推断出沥青混合料损伤开裂位置主要集中于竖向路径最大拉应力处。
最后,基于CT技术、DIP技术和FEM方法,利用软件Mimics对沥青混合料三维数值模型进行重构研究。并对比分析真实沥青混合料试件与数值模型内部结构中各组分在体积含量方面的差异,验证了该三维数值模型的正确性。
The macroscopic performance of asphalt mixture has a close correlation with its internal structural characteristics and components behaviors. Thus, it is quite essential to study on macroscopic performance of asphalt mixture from the microscopic perspective. Numerical simulation of mechanical behaviors experiments considering microscopic structure characteristics and its evolution, which combines macroscopic performance with components of asphalt mixture quantitatively, moreover, controls the balance between different mechanical behaviors of asphalt mixture, and saves extensive experiential laboratory test.
Firstly, the air voids distribution of three gradations of aggregate was characterized by using X-ray computed tomography and digital image processing technology based on the laboratory compaction methods of fabrication specimens in China. Furthermore, a mathematic model was made to present for describing the air voids distribution internal structure of asphalt mixtures by means of statistical analysis. The results showed that the gradation of aggregate and compaction methods had considerable influence on air voids distribution in the internal specimens, which was found to display symmetrical feature along the depth of Marshall specimen, whereby distribution of air voids in the static compacted specimen is nonsymmetrical along the depth, and the number of air voids on top part of a specimen was bigger than at bottom part. The number of air voids was more bigger and the fluctuations along the depth was more remarkable, the air voids size was almost consistent in static compacted specimens compared with the Marshall specimens in uniform gradation of aggregate. The statistical analysis performed validated the applicability of a two parameters mathematics model for characterizing air voids distribution of asphalt mixture, and the model could quantify the effect of compaction methods and gradation of aggregate on air voids.
In addition, according to the theory of viscoelasticity, with the technique of X-ray CT, DIP and FEM, the indirect tensile test and numerical creep test were conducted to two-dimension numerical model of asphalt mixture. The selection method for the location of the optimum test section was proposed through the analysis on the internal structural mechanical response of homogeneous model and heterogeneous model, meanwhile, the location of damage cracking of asphalt mixture and its reasons under the splitting load effect was analyzed. The results showed heterogeneous model simulated creep test accurately as compared with homogeneous model. Different sections along the height direction had no impact on the results of numerical test. Therefore, any section along this direction may become the optimum test section. Variation trend of S11curve and S22curve was identical for two models mentioned above. The maximum compressive stress of homogeneous model appeared on the pivot of the model, the maximum compressive stress of heterogeneous model appeared on the interface of mortar and coarse aggregate, and the compressive stress along vertical path was bigger than the compressive stress along horizontal path, thereby the internal location of damage cracking of asphalt mixture can be concluded on the maximum compressive stress along vertical path.
In the end, the reconstruction analysis on three-dimensional numerical model was performed using Mimics software based on X-ray CT, DIP and FEM. Additionally, a comparative analysis was carried out in terms of volume fraction of internal structural components of asphalt mixture specimen and numerical model, then the accuracy of three-dimensional numerical model was verified.
引文
[1]Buttlar W G, Roque R. Evaluation of empirical and theoretical model to determine asphalt mixture stiffnesses at low temperatures[J]. Journal of the Association of Asphalt Paving Technologists,1996, (2):99-141.
[2]Hashin Z. Viscoelastic behaviour of heterogeneous media[J]. Journal of Applied Mechanics, Trans ASME,1965, (9):630-636.
[3]Christensen R M, Lo K H. Solutions for effective shear properties in three phase sphere and cylinder models[J]. J Mech Phys Solids,1979, (27):315-330.
[4]Buttlar W G, Bozkurt D, Al-Khateeb G, Waldfoff A S. Understanding asphalt mastic behavior through micromechanics[J]. Journal of the Transportation Research Board, 1999, (1681):157-169.
[5]Shashidhar N, Needham S P, Chollar B H, Romero P. Prediction of the performance of mineral fillers in stone matrix asphalt[J]. Journal of the Association of Asphalt Paving Technologists,1996, (2):222-251.
[6]Cundall P A, Hart R D. Numerical modeling of discontinue[J]. Engineering Computations,1992,9(2):101-113.
[7]郝培文,程磊,林立.半柔性路面混合料路用性能[J].长安大学学报(自然科学版),2003,23(2):1-6.
[8]王辉,张起森.沥青混合料目标配合比设计方法[J].长安大学学报(自然科学版),2004,24(6):25-28.
[9]李强,马松林,王鹏飞.沥青路面冷再生混合料疲劳性能[J].交通运输工程学报,2004,4(1):7-10.
[10]王金昌,朱向荣.软土地基上含反射裂缝沥青道路的动力响应分析[J].中国公路学报,2004,17(1):1-6.
[11]王端宜.设计沥青路面及其方法研究[D]:(博士学位论文).广州:华南理工大学,2003.
[12]U S Department of Transportation. Simulation, imaging and mechanics of asphalt pavement[R]. Virginia:Turner-Fairbanks Highway Research Center,1998.
[13]胡霞光.沥青混合料细观力学分析综述[J].长安大学学报(自然科学版),2005,25(2): 6-10.
[14]曾国伟,杨新华,尹安毅,磨季云.沥青混合料损伤蠕变模型试验研究[J].武汉科技大学学报,2011,34(5):364-367.
[15]张久鹏,黄晓明.沥青混合料永久变形的弹黏塑-损伤力学模型[J].东南大学学报,2010,40(1):185-189.
[16]朱洪洲,严恒,唐伯明.沥青混合料疲劳-蠕变交互作用损伤模型[J].中国公路学报,2011,24(4):15-20.
[17]SIMAP Team. Simulation Imaging and Mechanics of Asphalt Pavements. U. S. FHWA. 1998, (6):1-3.
[18]SIMAP Team. Strategic Highway Research Program. Technical Brief of C-SHRP. U. S. FHWA.1995, (2):20-25.
[19]裴建中.沥青路面细观结构特性与衰变行为[M].北京:科学出版社,2010.
[20]Mora C, Kwan A, Chan H. Particles size distribution analysis of coarse aggregate using digital image processing[J]. Cement and Concrete Research,1998,97(1): 337-354.
[21]Kuo C Y, Rollings R S, Lynch L N. Morphological study of coarse aggregates using image analysis[J]. Journal of Materials in Civil Engineering,1998,10(3):135-142.
[22]Masad E, Muhunthan B, Shashidhar N, et al. Aggregate orientation and segregation in asphalt concrete[J]. Geotechnical Special publication,1998, (85):69-80.
[23]Masad E, Muhunthan B, Shashidhar N, et al. Internal structure characterization of asphalt concrete using image analysis [J]. Journal of Computing in Civil Engineering, 1999,13(2):88-95.
[24]Shashidhar N. X-ray tomography of asphalt concrete[J]. Journal of the Transportation Research Board,1999, (1681):186-192.
[25]Wang L B, Frost J, Shashidhar N. Mircostructure study of WesTrack mixes from X-ray tomography images[J]. Journal of the Transportation Research Board,2001, (1767):85-101.
[26]Al-Omari A, Tashman L, Masad E, et al. Proposed methodology for predicting HMA permeability[J]. Journal of the Association of Asphalt Paving Technologists,2002, 71(2):30-58.
[27]Masad E, Jandhyala V K, Dasgupta N, et al. Characterization of air void distribution in asphalt mixes using X-ray computed tomography[J]. Journal of Materials in Civil Engineering,2002,14(2):122-129.
[28]Masad E, Button J. Implication of experimental measurements and analyses of the internal structure of HMA[J]. Journal of the Transportation Research Board, 2004, (1891):212-220.
[29]张倩娜.基于数字图像处理技术的沥青混合料微观结构分析方法研究[D]:(博士学位论文).上海:同济大学,2000.
[30]李智.基于数字图像处理技术的沥青混合料体积组成特性分析[D]:(博士学位论文).哈尔滨:哈尔滨工业大学,2002.
[31]李智,徐伟,王绍怀,张肖宁.沥青混合料数字图像处理技术的方法研究[J].公路交通科技,2003,20(6):13-16.
[32]张肖宁,李智,虞将苗.沥青混合料体积组成及其数字图像处理技术[J].华南理工大学学报,2002,30(11):113-118.
[33]黄隆异.沥青混凝土巨观车辙及围观轨迹之行为机制分析[D]:(博士学位论文).台北:国立成功大学,2003.
[34]陈春,郝景贤.多空隙排水沥青混合料材料设计参数研究[J].公路,2003,10(10):91-93.
[35]陈春,许志鸿,陈兴伟.沥青混合料空隙率影响因素研究[J].公路,2003,4(4):111-113.
[36]李晓军,张肖宁.CT技术在沥青胶结颗粒材料内部结构分析中的应用[J].公路交通科技,2005,22(2):14-16.
[37]李芬,沈成武.基于CT图像的沥青混合料分形特征的研究[J].华中科技大学学报(城市科学版),2006,23(2):35-37.
[38]李芬,沈成武,杨吉新.沥青混凝土材料细观损伤的数值模拟[J].交通科技,2006,(214):56-58.
[39]张炳国,李芬,熊文林.沥青混凝土材料细观损伤演化研究[J].公路,2006,10(10):152-154.
[40]汪海年,郝培文.沥青混合料微细观结构的研究进展[J].长安大学学报,2008,3(28):11—15.
[41]裴建中,张嘉林.矿料级配对多孔沥青混合料空隙分布特征的影响[J].中国公路学报,2010,23(1):1-6.
[42]裴建中,王富玉,张嘉林.基于X-CT技术的多孔排水沥青混合料空隙竖向分布特性[J].吉林大学学报(工学版),2009,39(2):215-219.
[43]Sepehr K, Svec 0 J, Yue Z Q, et al. Finite Element modeling of asphalt concrete microstructure[C]. Proceeding of the 3rd International Conference on Computer-Aided Assessment and Control Localized Damage,1994.
[44]Chang K G, Meegoda J N. Micromechanical simulation of hot mix asphalt [J]. Journal of the Transportation Research Board,1997, (1757):111-118.
[45]Wang L B. An Evaluation of the Microstructures and the Macro-Behavior of Unbonded and Bonded Granular Materials[D]. Georgia:Georgia Institute of Technology,1998.
[46]Wang L B, Frost J, Mohammad L, et al. Three-dimensional aggregate evaluation using X-ray tomography imaging[C].81st Annual Meeting of Transportation Research Board,2002. Washington D. C.:1-22.
[47]Masad E, Tashman L., Somedavan N., et al. Micromechanics-based analysis of stiffness anisotropy in asphalt mixtures[J]. Journal of Materials in Civil Engineering,2002,14(5):374-383.
[48]You Z P. Development of a Microromechanical Modeling Approach to Predict Asphalt Mixture Stiffness Using the Discrete Element Method[D]. Urbana:University of Illinois at Urbana-Champaign,2003.
[49]Zhang P. Microstructure Generation of Asphalt Concrete and Lattice Modeling of its Cracking Behavior under Low Temperature[D]. Raleigh:North Carolina State University,2003.
[50]Wang L B, Mayer L, Mohammad L, et al. A micromechanics study on top-down cracking[J]. Journal of the Transportation Research Board,2003, (1853):121-133.
[51]Birgisson B, Soranakom C, Napier J, et al. Microstructure and fracture in asphalt mixtures using a boundary element approach[J]. Journal of Materials in Civil Engineering,2004,16(2):116-121.
[52]Masad E, Castelblanco A, Birgisson B. Effects of air void size distribution, pore pressure, and bond energy on moisture damage[J]. Journal of Testing and Evaluation,2006,34(1):15-23.
[53]杨新华,王习武,陈传尧,蒙培生.用图像处理技术实现沥青混合料有限元建模[J].中南公路工程,2005,30(3):5-7.
[54]虞将苗,李晓军,王端宜,张肖宁.基于计算机层析识别的沥青混合料有限元模型[J].长安大学学报(自然科学版),2006,26(1):16-19.
[55]黄碧霞,陆阳,张华.基于竖向识别的沥青混合料有限元建模[J].路基工程,2007,(135):5-6.
[56]汪海年,郝培文,吕光印.沥青混合料内部空隙分布规律[J].交通运输工程学报,2009,9(1):6-11.
[57]王端宜,吴文亮,张肖宁,虞将苗,李智.基于数字图像处理和有限元建模方法的沥青混合料劈裂试验数值模拟[J].吉林大学学报,2011,41(4):968-972.
[58]万成.基于X-ray CT和有限元方法的沥青混合料三维重构与数值试验研究[D]:(博士学位论文).广州:华南理工大学,2010.
[59]Masad E, Button J W. Unified imaging approach for measuring aggregate angularity and texture[J]. Computer Aided Civil and Infrastructure Engineering,2000,15(4): 273—280.
[60]邱延峻,闫常赫,艾长发.非均质沥青混合料劈裂试验全过程数值模拟[J].交通运输工程学报,2009,9(2):12-16.
[61]牟瀚林,王顺洪,朱敏.沥青混合料蠕变试验的数值模拟研究[J].公路交通科技,2008,10(5):17—20.
[62]张久鹏,黄晓明,高英.沥青混合料非线性蠕变模型及其参数确定[J].长安大学学报(自然科学版),2009,29(2):24-27.
[63]张久鹏,黄晓明,马涛.沥青混合料损伤蠕变特性及模型研究[J].岩土工程学报,2008,30(12):1867-1871.
[64]蔡峨.黏弹性力学基础[M].北京:北京航空航天大学出版社,1989.
[65]张肖宁.沥青与沥青混合料的黏弹性力学原理及应用[M].北京:人民交通出版社,2006.
[66]沈金安.沥青及沥青混合料路用性能[M].北京:人民交通出版社,2001.
[67]Wang L. B., Harold Skip Paul, Thomas Harman. Characterization of Aggregates and Asphalt Concrete using X-ray Computerized Tomography and Computational Techniques, AAPT, March 2004, Baton Rouge, Louiseana.
[68]Qingli Dai. Prediction of Dynamic Modulus and Phase Angle of Stone-Based Composites using A Micromechanical Finite Element Approach[J]. Journal of Materials in Civil Engineering,2009, (1061):1-25.
[69]张裕卿,黄晓明.基于微观力学的沥青混合料黏弹性预测[J].吉林大学学报(工学版),2008,40(1):52—57.