摘 要：结合小湾拱坝湿筛和三级配混凝土静态弯拉试验，采用全数字化声发射系统采集了两种混凝土在三点弯曲荷载作用下从加载至最终破坏的声发射特征参数和波形。对比分析了各加载阶段的声发射活动发展规律及声发射波形FFT功率谱峰值频率和频率质心的统计特征，识别了两种混凝土以声发射特征参数为基础的损伤断裂机制，采用商业声发射软件对微裂缝局部化区域进行了定位。结果表明，三级配混凝土与湿筛混凝土相比，具有以下声发射特征：(1)更易诱发损伤，在各个加载阶段具有较小的声发射b值；(2)声发射撞击峰值频率在100-125kHz频段及225-250kHz频段也有分布，同时频率质心比湿筛混凝土低；(3)在湿筛混凝土的一个特定机制的持续时间范围内，三级配混凝土识别为两个机制；(4)微裂缝的局部化区域范围大于湿筛混凝土。

Abstract：Combining with the Flexural-Tensile tests of wet sieving and three-graded concrete in Xiaowan arch dam., feature parameters and waveforms of acoustic emission (AE) signals during the whole process of third-point flexural-tensile are acquired using full-digital acoustic emission system. The development of acoustic emission activities in each loading stages is analyzed, the statistical features of peak frequency and frequency centroid calculated from FFT power spectrum are compared, damage mechanisms are identified based on the acoustic emission parameters, and the extent of the localized failure zones of microcracks are also compared using commercial software of AEwin, the following characteristics are found in three-graded concrete comparing with wet sieving concrete: (1)Easier to induce damage, and lower b value is observed in each loading stages; (2) The peak frequency of hits also appear in the frequency band of 100-125kHz and 225-250kHz, and the distribution of frequency centroid tends to lower than wet sieving concrete; (3) The duration ranges of two specific mechanisms identified in three-graded concrete are covered by one duration range in wet sieving concrete; (4) it showed a wider localized zone of microcracking than wet sieving concrete.