基于PFC3D的无砂混凝土强度及损伤模式
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摘要
为对无砂混凝土的强度及破坏损伤模式进行深入研究,借助离散元颗粒流软件PFC3D对无砂混凝土2种典型卵石骨料进行仿真建模,建立了7组孔隙率分别为0.26,0.28,0.30,0.32,0.34,0.36,0.38的无砂混凝土三维结构模型,模拟计算各组试块在单轴压缩试验下的受力及破坏情况。同时,对模型试块单轴试验中内部断裂发展情况进行监测统计。结果表明:随着模型孔隙率的增加,模型颗粒数、颗粒接触粘结数逐渐下降,抗压强度呈下降趋势;数值模拟曲线与多孔混凝土应力-应变曲线模型基本符合,与常规混凝土应力-应变曲线模型相比,在曲线上升阶段表现出更强的线性趋势,曲线下降段卸载迅速,体现出高脆性的特点;在模拟试验中,模型内部接触断裂多发生于模型边角及加载面处,在模型达到峰值强度后,断裂数急剧上升形成贯通的断裂面;根据峰值强度下断裂位置信息的统计分析定义了无砂混凝土"易破坏区",该区域体积为试块总体积的47.6%,包含断裂数达到总断裂数的69%以上。研究结果可为无砂混凝土的力学及损伤机理研究提供参考。
The strength and damage patterns of no-fines concrete are investigated with the help of PFC3 D. The three-dimensional structural models of no-fines concrete composed of two typical shapes of pebble aggregate are established with varied porosity(0.26, 0.28, 0.30, 0.32, 0.34, 0.36, and 0.38). The stress and deformation of each test block under uniaxial compression test are simulated. In the meantime, the development of internal fractures during the uniaxial test is monitored. Research results reveal that(1) with the increase of porosity, the number of particles and the number of particles in contact decrease gradually, and the uniaxial compressive strength of the model decreases also.(2) The stress-strain curve of no-fines concrete obtained from numerical simulation is consistent with that of porous concrete obtained by previous tests by other scholars, indicating that PFC could well simulate the stress-strain features of no-fines concrete. The uprising segment of stress-strain curve of no-fines concrete is more linear than that of conventional concrete; in the downward segment, unloading gets more swiftly, implying that no-fines concrete is highly brittle.(3) Mostly found in the vicinity of corners and loading surface, fractures of no-fines concrete intensifies with the increase of loading, and even expands dramatically until penetration after peak strength is reached.(4) In accordance with the locations of fractures at peak strength, the vulnerable zone of no-fines concrete is defined as the part left when inscribed sphere is removed, which accounts for 47.6% of the total volume of test block, and in which fractures takes up over 69%. The research findings offer reference for the study of mechanics and damage mechanism of no-fines concrete.
The strength and damage patterns of no-fines concrete are investigated with the help of PFC3 D. The three-dimensional structural models of no-fines concrete composed of two typical shapes of pebble aggregate are established with varied porosity(0.26, 0.28, 0.30, 0.32, 0.34, 0.36, and 0.38). The stress and deformation of each test block under uniaxial compression test are simulated. In the meantime, the development of internal fractures during the uniaxial test is monitored. Research results reveal that(1) with the increase of porosity, the number of particles and the number of particles in contact decrease gradually, and the uniaxial compressive strength of the model decreases also.(2) The stress-strain curve of no-fines concrete obtained from numerical simulation is consistent with that of porous concrete obtained by previous tests by other scholars, indicating that PFC could well simulate the stress-strain features of no-fines concrete. The uprising segment of stress-strain curve of no-fines concrete is more linear than that of conventional concrete; in the downward segment, unloading gets more swiftly, implying that no-fines concrete is highly brittle.(3) Mostly found in the vicinity of corners and loading surface, fractures of no-fines concrete intensifies with the increase of loading, and even expands dramatically until penetration after peak strength is reached.(4) In accordance with the locations of fractures at peak strength, the vulnerable zone of no-fines concrete is defined as the part left when inscribed sphere is removed, which accounts for 47.6% of the total volume of test block, and in which fractures takes up over 69%. The research findings offer reference for the study of mechanics and damage mechanism of no-fines concrete.
引文
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[12] 宿辉,唐阳,聂汉江.基于PFC2D不同细观参数对生态混凝土宏观破坏分析[J].科学技术与工程,2014,14(28):118-124.
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[16] 康政,唐欣薇,秦川,等.基于细观离散元的混凝土端部效应分析[J].哈尔滨工业大学学报,2013,45(12):94-98.
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[19] 熊耀清,姚谦峰.轻质多孔混凝土受压应力-应变全曲线试验研究[J].四川建筑科学研究,2010,36(2):228-232.
[20] 过镇海,张秀琴,张达成,等.混凝土应力-应变全曲线的试验研究[J].建筑结构学报,1982,3(1):1-12.
[21] 张骥.混凝土塑性-损伤本构模型研究[D].武汉:华中科技大学,2010.
[2] 段吉鸿,王琳,张学森,等.几种适合在红河州生态混凝土中生长的草本植物对重金属的富集[J].长江科学院院报,2016,33(8):34-37.
[3] 王展展.透水混凝土力学性能的试验研究与数值模拟[D].武汉:武汉轻工大学,2015.
[4] BAZANT Z P,OH B H.Microplane Model for Progressive Fracture of Concrete and Rock[J].Journal of Engineering Mechanics,1985,111(4):559-582.
[5] 杨延毅,周维垣.岩石与混凝土类材料断裂过程研究[J].水力学报,1992,(11):69-74.
[6] 徐阳.多孔生态混凝土细观层次数值模拟研究[D].镇江:江苏大学,2016.
[7] 刘光廷,王宗敏.用随机骨料模型数值模拟混凝土材料的断裂[J].清华大学学报(自然科学版),1996,36(1):84-89.
[8] CUNDALL P A,STRACK O D L.A Discrete Numerical Model for Granular Assemblies[J].Geotechnique,1979,29(1):47-65.
[9] CUNDALL P A.Computer Model for Simulating Progressive Large-scale Movements in Blocky Systems[C]//Symposium of the International Society of Rock Mechanics,Nancy,France,October 4-6,1971:2-8.
[10] CUNDALL P A,HART R D.Numerical Modeling of Discontinue[J].Engineering Computation,1992,9(2):101-113.
[11] 王云飞,郑晓娟,王立平,等.粗骨料对混凝土单轴抗压强度及破坏特征影响的数值分析[J].硅酸盐通报,2016,35(9):2759-2766.
[12] 宿辉,唐阳,聂汉江.基于PFC2D不同细观参数对生态混凝土宏观破坏分析[J].科学技术与工程,2014,14(28):118-124.
[13] 张正珺,刘军,胡文,等.混凝土材料破坏过程的二维离散元模拟[J].水力发电学报,2010,29(5):22-27.
[14] Itasca Consulting Group.PFC2D(Particle Flow Code in Two-dimensions) Fish in PFC2D[R].Minneapolis,USA:Itasca Consulting Group,2008.
[15] FAKHIMI A,VILLEGAS T.Application of Dimensional Analysis in Calibration of a Discrete Element Model for Rock Deformation and Fracture[J].Rock Mechanics and Rock Engineering,2007,40(2):193-211.
[16] 康政,唐欣薇,秦川,等.基于细观离散元的混凝土端部效应分析[J].哈尔滨工业大学学报,2013,45(12):94-98.
[17] POTYONDY D O,CUNDALL P A.A Bonded-particle Model for Rock[J].International Journal of Rock Mechanics and Mining Sciences,2004,41(8):1329-1364.
[18] 谢新生,汤巍,王锦叶.多孔生态混凝土强度与孔隙率的试验研究[J].四川大学学报(工程科学版),2008,40(6):22-26.
[19] 熊耀清,姚谦峰.轻质多孔混凝土受压应力-应变全曲线试验研究[J].四川建筑科学研究,2010,36(2):228-232.
[20] 过镇海,张秀琴,张达成,等.混凝土应力-应变全曲线的试验研究[J].建筑结构学报,1982,3(1):1-12.
[21] 张骥.混凝土塑性-损伤本构模型研究[D].武汉:华中科技大学,2010.
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