冲击荷载作用下含黏结界面混凝土破坏特征与应力应变分析

Mechanical Characteristics and Stress and Strain Analysis of Concrete with Bonding Interface Under Impact Load

为研究冲击荷载下板式无砟轨道结构蒸养混凝土与自密实混凝土层间界面的破坏行为,利用分离式霍普金森杆(SHPB)对含黏结界面混凝土进行冲击试验,并就其破坏特征和应力应变全曲线特性以及损伤本构方程进行探讨.结果表明:含黏结界面混凝土在动态冲击荷载作用下存在界面脱黏分离和整体破碎两种失效模式.界面脱黏分离失效模式下,随着应变率的增加,含黏结界面混凝土的动态抗压强度、强度动态提高因子(DIF)、峰值应变、冲击韧性均增加,具有明显的应变率敏感性;整体破碎失效模式下,界面脱黏变形和破碎变形同时存在,随着应变率的增加,裂纹向界面区域累积、拓展,界面起到了能量缓冲的作用,此时含黏结界面混凝土动态抗压强度、DIF基本不变,而峰值应变和冲击韧性增加.所建立的基于Weibull分布的本构模型与试验结果吻合较好,尤其对峰前应力应变曲线有很好的匹配性.

To study the dynamic mechanical characteristic of steam cured concrete and self-compacting concrete bonding interface, a split Hopkinson pressure bar(SHPB) test was used to evaluate the dynamic properties of concrete with a bonding interface. The failure pattern and the characteristics of stress-strain curves and a constitutive model of concrete with a bonding interface were discussed. The results show that the impact destructions are associated with two forms of failures, i.e., the interface separation failure and concrete crushed failure. In interface separation failure, the peak stress, dynamic increase factor(DIF), peak strain, and impact toughness of concrete with a bonding interface increase with the increase of strain rate, and the concrete with a bonding interface shows a stronger strain rate sensitivity. In concrete crushed failure, there exist debonding deformation and crush deformation exist simultaneously. With the increase of strain rate, the accumulation and development of crack at the interface could make the interface zone play an energy relieving role in concrete with a bonding interface. The peak stress and the DIF of concrete with a bonding interface remain unchanged, while the peak strain and impact toughness both increase. The calculated data by the established dynamic constitutive model are similar to the experimental results, especially before the ultimate state of strain stress curves.