不同缝高比大坝混凝土断裂性能及声发射特性

Fracture Performance and Acoustic Emission Characteristics of Dam Concrete with Different Crack-depth Ratios

为研究缝高比对大坝混凝土断裂性能的影响,对不同缝高比(0.3、0.4、0.5)的带缺口立方体大坝混凝土试件(边长为300、450 mm)分别开展楔入劈拉试验,同时采用声发射技术监测大坝混凝土的声发射特性。根据试验结果获得了荷载-裂缝口张开位移(P-CMOD)曲线、断裂韧度、断裂能及声发射特征参数。研究结果表明,300、450 mm立方体大坝混凝土试件的起裂韧度均与缝高比无关,可视为一常数;而失稳断裂韧度随缝高比的增大而减小。随着缝高比的增大,试件的断裂能、临界裂缝扩展量、声发射累积撞击数和振铃计数逐渐减小。声发射累计振铃计数和累计撞击次数四阶段特征不仅可反映大坝混凝土四阶段破坏过程,也能够反映其断裂破坏的边界效应;声发射b值可反映大坝混凝土峰后损伤破坏的两个阶段。

In order to study the fracture performance of wedge split tensile specimens with different crack-depth ratios, two types of notched cubic concrete specimens with dimensions of 300 mm and 450 mm under different crack-depth ratios(0.3, 0.4, 0.5) were respectively carried out wedge split tensile tests. At the same time, acoustic emission technology was used to monitor the acoustic emission(AE) characteristics of dam concrete. Based on the test results, the curve of load-crack mouth opening displacement(P-CMOD), fracture toughness, fracture energy and acoustic emission characteristic parameters were obtained. The results show that the crack initiation toughness of the 300 mm and 450 mm cube dam concrete specimens are independent of the crack-depth ratio and can be regarded as a constant, while the fracture toughness decrease with the increase of the crack-depth ratio. As the crack-depth ratio increases, the fracture energy, the critical crack length, the AE cumulative counts and hits decrease. Besides, the AE cumulative counts and hits can reflect not only the four-stage fracture process of dam concrete, but also the boundary effect of dam concrete. The acoustic emission value b can reflect the two stages of post-peak damage and destruction of the dam concrete.