多场耦合下路面混凝土细观裂缝的演化规律
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摘要
细观裂缝的演化与空间展布规律是影响路面混凝土耐久性的关键因素.为明确寒冷地区路面混凝土在实际工作环境下结构内部微裂缝的萌生、扩展、压缩等演化规律,基于多场疲劳试验,针对路面混凝土内部结构进行了SEM、CT扫描及图像分割,通过对比分析荷载单场、荷载-冻融双场及荷载-冻融-干湿循环三场耦合下的裂缝面积密度、平均裂缝宽度、最大裂缝长度及盒分形维数特征,从细观尺度揭示了不同荷载水平、耦合方案下微裂缝的动态损伤发展规律.结果表明:单荷载作用下,随荷载次数增加,最大裂缝长度呈萌生-闭合-延伸交替变化,宽度表现为压缩-扩张交替变化,分形维数先增后减;荷载-冻融双场耦合引发的结晶膨胀应力促使裂缝面积密度及最大裂缝长度单调增加,80%荷载水平时,混凝土在较小裂缝长度、宽度下便发生疲劳破坏;荷载-冻融-干湿循环三场耦合下,附加干缩应力沿裂缝方向产生收缩应力,在垂直裂缝方向产生压缩应力,促使裂缝沿长度方向延伸,宽度减小,同时伴随更多微裂缝成核.
The evolution and spatial distribution rule of microcosmic cracks are two key factors affecting the durability of pavement concrete. In order to explore the evolution of microcracks initiation,propagation and compression for pavement concrete in actual working environment in cold regions,multi-field fatigue tests were conducted,and SEM,CT and image segmentation techniques were adopted to compare the crack characteristics such as area density,average width,maximum length and fractal dimension for specimens respectively in a single field,in double fields and in three-field coupling condition. Then,the dynamic damage rules of microcracks under different loading levels and with different coupling schemes were discussed in meso scale. The results show that( 1) under the action of single load,the maximum length of cracks shows a "initiating-closing-extending"trend,while the average width reveals a "compressing-expanding"trend,and the fractal dimension first increases and then decreases with the increase of loading cycles;( 2) the crystallization swelling stress initiated by loading-freezing-thawing coupling effect makes the crack area density and the maximum crack length both increase,and the concrete reveals fatigue failure with small crack length and width under 80% loading condition;( 3) under the loading-freezing-thawingwetting-drying three-field coupling condition,the additional dry shrinkage stress causes a shrinkage stress in the parallel direction of the crack and a compressive stress in the vertical direction of the crack,which makes the crack length increase,the crack width decrease,and more micro-cracks nucleate.
The evolution and spatial distribution rule of microcosmic cracks are two key factors affecting the durability of pavement concrete. In order to explore the evolution of microcracks initiation,propagation and compression for pavement concrete in actual working environment in cold regions,multi-field fatigue tests were conducted,and SEM,CT and image segmentation techniques were adopted to compare the crack characteristics such as area density,average width,maximum length and fractal dimension for specimens respectively in a single field,in double fields and in three-field coupling condition. Then,the dynamic damage rules of microcracks under different loading levels and with different coupling schemes were discussed in meso scale. The results show that( 1) under the action of single load,the maximum length of cracks shows a "initiating-closing-extending"trend,while the average width reveals a "compressing-expanding"trend,and the fractal dimension first increases and then decreases with the increase of loading cycles;( 2) the crystallization swelling stress initiated by loading-freezing-thawing coupling effect makes the crack area density and the maximum crack length both increase,and the concrete reveals fatigue failure with small crack length and width under 80% loading condition;( 3) under the loading-freezing-thawingwetting-drying three-field coupling condition,the additional dry shrinkage stress causes a shrinkage stress in the parallel direction of the crack and a compressive stress in the vertical direction of the crack,which makes the crack length increase,the crack width decrease,and more micro-cracks nucleate.
引文
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[2]李金平,章金钊,盛煜.冻土区水泥和沥青路面病害分布规律探讨[J].公路交通科技,2010,27(7):18-24.LI Jin-pin,ZHANG Jin-zhao,SHENG Yu.Study on distribution patterns of distresses in cement concrete pavement and asphalt pavement in permafrost regions[J].Journal of Highway and Transportation Research and Development,2010,27(7):18-24.
[3]谈至明,姚祖康.水泥混凝土路面疲劳温度应力的计算[J].中国公路学报,1994(1):1-7.TAN Zhi-ming,YAO Zu-kang.The estimation of fatiguethermal stress of concrete pavements[J].China Journal of Highway and Transport,1994(1):1-7.
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[9]刘问,徐世烺,李庆华.等幅疲劳荷载作用下超高韧性水泥基复合材料弯曲疲劳寿命试验研究[J].建筑结构学报,2012,33(1):119-127.LIU Wen,XU Shi-lang,LI Qing-hua.Study on flexural fatigue life of ultrahigh toughness cementitious composites under constant amplitude cyclic loading[J].Journal of Building Structures,2012,33(1):119-127.
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[12]李兆霞.损伤力学及其应用[M].北京:科学出版社,2002.
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[14]LI Wen-ting,SUN Wei,JIANG Jin-yang.Damage of concrete experiencing flexural fatigue load and closed freeze/thaw cycles simultaneously[J].Construction and Building Materials,2011,25(5):2604-2610.
[15]赵爱红,虞吉林.准脆性材料的细观损伤演化模型[J].清华大学学报(自然科学版),2000,40(50):88-91.ZHAO Ai-hong,YU Ji-lin.A micro-mechanical damage model for quasi-brittle materials[J].Journal of Tsinghua University(Sci&Tech),2000,40(50):88-91.
[16]田威,党发宁,陈厚群.基于CT图像处理技术的混凝土细观破裂分形分析[J].应用基础与工程科学学报,2012,20(3):424-431.TIAN Wei,CHANG Fa-ning,CHEN Hou-qun.Fractal analysis on meso-fracture of concrete based on the technique of CT image processing[J].Journal of Basic Science and Engineering,2012,20(3):424-431.
[17]李曙光,陈改新,鲁一晖.基于微裂纹定量分析的混凝土冻融损伤评价方法[J].水力发电学报,2013,32(3):207-212.LI Shu-guang,CHEN Gai-xin,LU Yi-hui.Evaluation method for freezing-thawing damage in concrete based on quantitative microcrack analysis[J].Journal of Hydroelectric Engineering,2013,32(3):207-212.
[18]韦江雄,余其俊,曾小星,等.混凝土中孔结构的分形维数研究[J].华南理工大学学报(自然科学版),2007,35(2):121-124.WEI Jiang-xiong,YU Qi-jun,ZENG Xiao-xing,et al.Fractal dimension of pore struture of concrete[J].Journal of South China University of Technology(Natural Science Edition),2007,35(2):121-124.
[19]郭伟,秦鸿根,陈惠苏,等.分形理论及其在混凝土材料研究中的应用[J].硅酸盐学报,2010,38(7):1362-1368.GUO Wei,QIN Hong-gen,CHEN Hui-su,et al.Fractal theory and its applications in the study of concrete materials[J].Journal of the Chinese Ceramic Society,2010,38(7):1362-1368.
[2]李金平,章金钊,盛煜.冻土区水泥和沥青路面病害分布规律探讨[J].公路交通科技,2010,27(7):18-24.LI Jin-pin,ZHANG Jin-zhao,SHENG Yu.Study on distribution patterns of distresses in cement concrete pavement and asphalt pavement in permafrost regions[J].Journal of Highway and Transportation Research and Development,2010,27(7):18-24.
[3]谈至明,姚祖康.水泥混凝土路面疲劳温度应力的计算[J].中国公路学报,1994(1):1-7.TAN Zhi-ming,YAO Zu-kang.The estimation of fatiguethermal stress of concrete pavements[J].China Journal of Highway and Transport,1994(1):1-7.
[4]焦修刚,刘光廷.混凝土热湿耦合数值计算中的参数拟合[J].清华大学学报(自然科学版),2005,45(3):319-321.JIAO Xiu-gang,LIU Guang-ting.Parameter fitting in numerical analysis of coupled heat and mass transport in concrete[J].Journal of Tsinghua University(Sci&Tech),2005,45(3):319-321.
[5]王秉纲,王选仓,高维成,等.重载水泥混凝土路面疲劳关系研究[C]∥中国公路学会2000学术年会暨五届二次理事会论文集.海口:中国公路出版社,2000:112-116.
[6]袁宏,姚祖康.考虑温度应力和荷载应力共同作用的混凝土路面结构设计方法[J].同济大学学报,1986,14(4):479-490.YUAN Hong,YAO Zu-kang.The structure design method of concrete pavement considering the combination of temperature stress and load stress[J].Journal of Tongji University,1986,14(4):479-490.
[7]TROTTIER J F,FORGERON D.Cumulative effects of flexural fatigue loading and freezing and thawing cycles on the flexural toughness of the fiber reinforced concrete[C]∥Proceedings of the Third International Conference on Concrete Under Severe Conditions:Environment and Loading.Vancouver,BC:ACM,2001:18-20.
[8]吴国雄.水泥混凝土路面开裂机理及破坏过程研究[D].重庆:西南交通大学,2003.
[9]刘问,徐世烺,李庆华.等幅疲劳荷载作用下超高韧性水泥基复合材料弯曲疲劳寿命试验研究[J].建筑结构学报,2012,33(1):119-127.LIU Wen,XU Shi-lang,LI Qing-hua.Study on flexural fatigue life of ultrahigh toughness cementitious composites under constant amplitude cyclic loading[J].Journal of Building Structures,2012,33(1):119-127.
[10]GOEL S,SINGH S P,SINGH P.Flexural fatigue strength and failure probability of self compacting fibre reinforced concrete beams[J].Engineering Structures,2012,40:131-140.
[11]胡昌斌,曾惠珍,阙云.湿热地区水泥混凝土路面温度场与温度应力研究[J].福州大学学报(自然科学版),2011,39(5):727-737.HU Chang-bin,ZENG Hui-zhen,QUE Yun.Characteristics of concrete pavement temperature field and temperature stress in hot and humid areas[J].Journal of Fuzhou University(Natural Science Edition),2011,39(5):727-737.
[12]李兆霞.损伤力学及其应用[M].北京:科学出版社,2002.
[13]吕惠卿,张湘伟,张荣辉.水泥混凝土路面断裂破坏研究[J].重庆交通大学学报(自然科学版),2010,29(1):54-57.LHui-qing,ZHANG Xiang-wei,ZHANG Rong-hui.Crack damage of cement concrete pavement[J].Journal of Chongqing Jiaotong University(Natural Science),2010,29(1):54-57.
[14]LI Wen-ting,SUN Wei,JIANG Jin-yang.Damage of concrete experiencing flexural fatigue load and closed freeze/thaw cycles simultaneously[J].Construction and Building Materials,2011,25(5):2604-2610.
[15]赵爱红,虞吉林.准脆性材料的细观损伤演化模型[J].清华大学学报(自然科学版),2000,40(50):88-91.ZHAO Ai-hong,YU Ji-lin.A micro-mechanical damage model for quasi-brittle materials[J].Journal of Tsinghua University(Sci&Tech),2000,40(50):88-91.
[16]田威,党发宁,陈厚群.基于CT图像处理技术的混凝土细观破裂分形分析[J].应用基础与工程科学学报,2012,20(3):424-431.TIAN Wei,CHANG Fa-ning,CHEN Hou-qun.Fractal analysis on meso-fracture of concrete based on the technique of CT image processing[J].Journal of Basic Science and Engineering,2012,20(3):424-431.
[17]李曙光,陈改新,鲁一晖.基于微裂纹定量分析的混凝土冻融损伤评价方法[J].水力发电学报,2013,32(3):207-212.LI Shu-guang,CHEN Gai-xin,LU Yi-hui.Evaluation method for freezing-thawing damage in concrete based on quantitative microcrack analysis[J].Journal of Hydroelectric Engineering,2013,32(3):207-212.
[18]韦江雄,余其俊,曾小星,等.混凝土中孔结构的分形维数研究[J].华南理工大学学报(自然科学版),2007,35(2):121-124.WEI Jiang-xiong,YU Qi-jun,ZENG Xiao-xing,et al.Fractal dimension of pore struture of concrete[J].Journal of South China University of Technology(Natural Science Edition),2007,35(2):121-124.
[19]郭伟,秦鸿根,陈惠苏,等.分形理论及其在混凝土材料研究中的应用[J].硅酸盐学报,2010,38(7):1362-1368.GUO Wei,QIN Hong-gen,CHEN Hui-su,et al.Fractal theory and its applications in the study of concrete materials[J].Journal of the Chinese Ceramic Society,2010,38(7):1362-1368.