摘要
研究了不同骨料体积分数下的混凝土增韧机制,建立了Ⅱ_(ⅡC)型断裂韧度K的细观力学模型。对含有4种骨料体积分数(19vol%、25vol%、31vol%、37vol%)的混凝土试件,分别进行了楔入劈拉试验和无切口试件的Ⅱ型断裂试验,并利用内聚力模型及点阵法对相关Ⅱ型断裂试验开展了细观模拟。结果表明:随着骨料体积分数的增加,混凝土Ⅰ型断裂韧度K_(ⅠC)和Ⅱ型断裂韧度K_(ⅡC)均明显提高,K_(ⅡC)/K_(ⅠC)逐渐增大且与骨料体积分数之间存在对数函数关系;骨料的圈闭-桥联对混凝土增韧起着主导作用,其增韧效应远大于裂纹路径偏转或裂尖屏蔽引起的;给出了Ⅱ型断裂韧度K_(ⅡC)和骨料体积分数V_(a)之间的细观力学关系,其预测值和试验值的符合性较好;混凝土Ⅱ型断裂细观模拟的力学响应、断裂形态和试验结果表现出良好的一致性;内聚力单元的标量刚度退化(Scalar stiffness degradation,S)值的变化,可用来表征混凝土在细观水平上的损伤演化,且对宏观断裂响应的预测有着重要作用。
The toughening mechanism of concrete with different aggregate volume fractions was investigated, and the meso-mechanical model of mode Ⅱ_(ⅡC) fracture toughness Kwas developed. The wedge splitting tests and mode Ⅱ fracture tests for non-notched specimens were carried out simultaneously for concrete specimens which were prepared with aggregates in different volume fractions of 19vol%, 25vol%, 31vol% and 37vol%. The meso-scale simulations of corresponding mode Ⅱ fracture tests were also performed by the cohesive zone model combined with the dot matrix method. The results show that as the aggregate volume fraction increases, the mode Ⅰ fracture toughness K_(ⅠC), mode Ⅱ fracture toughness K_(ⅡC) and the values of K_(ⅡC)/K_(ⅠC)increase significantly. It was further found that the relationship between the values of K_(ⅡC)/K_(ⅠC)and aggregate volume fraction can be described by a logarithmic function.The trapping-bridging of aggregate plays a leading role in the toughening of concrete, and its toughening effect is much greater than that caused by crack deflection or crack shielding. The meso-mechanical relation between Kand aggregate volume fraction was developed, and its prediction agrees well with the experimental data. The mecha-nical response and fracture morphology from meso-scale simulation of mode Ⅱ fracture of concrete are in good agreement with those of experimental tests. Furthermore, the scalar stiffness degradation(S) development of the cohesive element can be utilized to characterize the damage evolution of concrete at meso-level, which is valuable to the prediction of macro performance.
作者
陈燕伟
冯吉利
朱天宇
李凤晨
CHEN Yanwei;FENG Jili;ZHU Tianyu;LI Fengchen(State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,Beijing 100083,China;School of Mechanics and Civil Engineering,China University of Mining and Technology,Beijing 100083,China)
出处
《复合材料学报》
EI
CAS
CSCD
北大核心
2022年第10期4972-4987,共16页
Acta Materiae Compositae Sinica
基金
国家重点研发计划(2016YFC0600901)
国家自然科学基金(41172116,U1261212)。
关键词
骨料体积分数
增韧机制
断裂韧度
内聚力单元
损伤演化
细观力学模型
aggregate volume fraction
toughening mechanism
fracture toughness
cohesive element
damage evolution
meso-mechanical model
