基于颗粒流法研究混凝土的劈裂拉伸破坏特性

基于二维颗粒流程序，构建了包含水泥砂浆、不规则多边形骨料和水泥砂浆与骨料的交界面的二维混凝土细观模型，采用标定后的平节理模型参数，对混凝土破坏的裂纹演化和破坏机理进行研究. 模拟结果表明:宏观破坏的细观机制是水泥砂浆、骨料以及交界面内的裂纹扩展和演化造成的；随机骨料的分布会对混凝土的峰值应力和破坏模式有一定的影响；巴西圆盘试件内的裂纹起始于加载端，随着载荷增加裂纹向中心扩展，混凝土试件呈现出劈裂拉伸破坏的模式；随着加载速度的提高，沿加载方向上的主裂纹及其他次生裂纹相互作用，使混凝土试件出现大量的碎块；裂纹统计结果显示，在细观层次上，拉伸型裂纹主导了混凝土试件的劈裂破坏，少量的剪切型裂纹主要集中在试件加载端的骨料附近. 

Study on the Splitting Tensile Failure Characteristics of Concrete Based on the Particle Flow Method

Based on the two-dimensional particle flow program, a two-dimensional concrete mesoscopic model was established including cement mortar, irregular polygonal aggregate and the interface (ITZ) between cement mortar and aggregate. The crack evolution and failure mechanism of fracture concrete was investigated using the calibrated flat joint model parameters. The simulation results indicate that the meso-mechanism of the macroscopic failure is induced by the crack propagation and evolution in the cement mortar, aggregate and ITZ. In addition, the distribution of random aggregates has an impact on the peak stress and failure mode of concrete at a certain level. The crack in the Brazilian disc specimen is generated at the loading end, and expands to the center of the specimen as the load increases. Finally, a split tensile failure mode appears in the concrete specimen. Moreover, as the loading speed increases, a large number of fragments in the concrete specimen are generated due to the interaction between the main cracks along the loading direction and other secondary cracks. The statistical results of cracks indicate that tensile cracks dominate the split failure of concrete specimens at the mesoscopic level. At the same time, a few shear cracks are mainly generated near the aggregate at the loading end of the specimen.