骨料-界面裂纹相互作用对混凝土开裂强度的影响  

Effect of aggregate-interface crack interaction on cracking strength of concrete

作　　者：吕从聪 卢晓春 熊勃勃[1,2] 尹月明 LÜCongcong;LU Xiaochun;XIONG Bobo;YIN Yueming(Hubei Key Laboratory of Construction and Management in Hydropower Engineering,China Three Gorges University,443002,Yichang,China;College of Hydraulic and Environmental Engineering,China Three Gorges University,443002,Yichang,China;State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin,China Institute of Water Resources and Hydropower Research,100038,Beijing,China)

机构地区：[1]三峡大学湖北省水电工程施工与管理重点实验室,宜昌443002 [2]三峡大学水利与环境学院,宜昌443002 [3]中国水利水电科学研究院流域水循环模拟与调控国家重点实验室,北京100038

出　　处：《应用力学学报》2021年第6期2329-2337,共9页Chinese Journal of Applied Mechanics

基　　金：国家重点研发计划项目(2017YFC405101-2);国家自然科学基金项目(52009068);湖北省水电工程施工与管理重点实验室(三峡大学)开放基金(2020KSD13)。

摘　　要：混凝土中骨料、界面裂纹在荷载作用下相互影响,引起界面黏结裂纹扩展并形成脱黏,从而对混凝土开裂强度产生较大影响。采用等效平均的方法考虑骨料与界面裂纹之间的相互作用,首先将骨料和界面弧形裂纹视为两类夹杂,并基于相互作用直推法,得到外荷载和热残余应力共同作用下夹杂周围的平均应力及作用于砂浆基体的等效应力。然后利用该应力边界条件和Prasad公式求得圆形骨料界面裂纹的应力强度因子,通过改进复合压剪状态下I型裂纹应力强度因子的取值,修正界面裂纹开裂扩展时的能量释放率,并以此作为反映混凝土开裂强度的指标。通过与数值结果以及单一夹杂理论解的比较,验证了公式的有效性。最后结合算例,进一步探讨了骨料-界面裂纹相互作用、热残余应力等对混凝土开裂强度的影响规律。结果表明:考虑骨料-裂纹相互作用增大了界面裂纹的应力强度因子和能量释放率,使混凝土更易于开裂破坏;弧形裂纹的影响并非单调且比较复杂,存在最不利的裂纹长度,当裂纹长度达到一定值时,甚至可能出现张开、闭合状态的转变;残余应力的存在降低了混凝土的强度,对界面裂纹扩展影响显著,可通过改善骨料级配、热膨胀系数、以及智能调控混凝土温差变化等方法加以控制。Aggregate and interface crack in concrete interact under load, which leads to interface bond crack spreading and debonding, greatly affecting cracking strength of concrete. First, aggregate and interface arc cracks are regarded as two types of inclusions. Based on the direct inference method of interaction, we obtained the average stress around the inclusions and the equivalent stress acting on the mortar matrix under the combined action of external load and thermal residual stress. Then, the stress intensity factor of circular aggregate interface cracks is obtained by using this stress boundary condition and Prasad formula. By improving the value of I-mode crack stress intensity factor under composite compression-shear state, the energy release rate of interface crack propagation is modified, which is used as an index to reflect the cracking strength of concrete. By comparing them with numerical results and single inclusion theoretical solution, the validity and correctness of the formula are verified. Finally, using an example, the paper further discusses the influence of aggregate-interface crack interaction and thermal residual stress on the cracking strength of concrete. The results show that considering the interaction between aggregate and crack increases the stress intensity factor and energy release rate of interface crack,which makes concrete easier to crack and destroy. The influence of arc crack is not monotonous and complex, and there is the most unfavorable crack length. When the crack length reaches a certain value, the transition of opening and closing state may even appear. The existence of residual stress reduces the strength of concrete and significantly affects the interface crack propagation, which can be controlled by improving aggregate gradation and thermal expansion coefficient and intelligently adjusting the temperature difference of concrete.

关 键 词：混凝土 骨料裂纹相互作用 热残余应力 相互作用直推法 开裂强度 

分 类 号：TV313[水利工程—水工结构工程]