为研究超高性能混凝土（UHPC）的劈拉破坏特征，采用3种不同的加载速率（0.1、0.01、0.001 mm/s）进行劈拉加载，在加载过程中采用数字图像相关（DIC）方法非接触观测裂缝演化，同时结合声发射（AE）技术对UHPC的破坏全过程进行动态监测，并基于DIC应变云图、AE参量分析试件的破坏特征。结果表明，钢纤维的掺入改善了混凝土的脆性，UHPC峰后荷载-位移曲线下降更平缓，没有出现急剧下降的情况；加载速率越高，UHPC测出劈拉强度越高，符合混凝土速率效应规律，加载速率由0.001 mm/s提升到0.01 mm/s和由0.01 mm/s提升到0.1 mm/s，劈拉峰值荷载分别提高了27.9%和28.5%。采用DIC法进行UHPC劈拉试验的变形测量可获得连续的变形数据，能完整地捕捉裂缝的开展过程，证明DIC能很好地反映试件表面裂缝开展演化过程。基于RA-AF值分析可以快捷、有效地判断混凝土中裂缝的开展类型。根据分析结果，UHPC劈拉试验的裂缝类型绝大多数为拉伸裂缝，且随着加载速率的提高，拉伸裂缝占总裂缝的比例提高。

In order to study the splitting tensile failure characteristics of ultra-high performance concrete (UHPC), three different loading rates (0.1, 0.01, 0.001 mm/s) were used for the splitting tensile loading. During the loading process, the digital image correlation (DIC) method was used to observe the crack evolution by non-contact deformation. At the same time, the acoustic emission (AE) technology was used to dynamically monitor the entire failure process of UHPC, and the failure characteristics of the specimen were analyzed based on the DIC strain cloud map and AE parameters. The results show that due to the incorporation of steel fibers, the brittleness of concrete is improved, and the post-peak load-displacement curve of UHPC decreases more gently without a sharp decline. The higher the loading rate, the higher the splitting tensile strength measured by UHPC, which conforms to the law of concrete rate effect. When the loading rate is increased from 0.001 mm/s to 0.01 mm/s and from 0.01 mm/s to 0.1 mm/s, the splitting tensile peak load is increased by 27.9 % and 28.5 % respectively. The digital image correlation method is used to measure the deformation of UHPC splitting tensile experiment, and continuous deformation data can be obtained, which can completely capture the development process of cracks. It is proved that DIC can well reflect the evolution process of cracks on the surface of specimens. The analysis based on RA-AF value can quickly and effectively determine the type of crack development in concrete. According to the analysis results, the crack types of UHPC splitting tensile experiment are mostly tensile cracks, and the proportion of tensile cracks in the total cracks increases with the increase of loading rate.

TU528.58

国家重点研发计划（2021YFB2600200）；国家自然科学基金（51979090、52379124）