利用我国西南部某特高拱坝施工现场的拌合楼,浇筑成型骨料最大粒径150 mm的大坝混凝土楔入劈拉试件,试件尺寸分别为800 mm×800 mm×450 mm、1 000 mm×1000 mm×450 mm和1 200 mm×1 200 mm×450mm。通过试验获得现场浇筑大坝混凝土试件的起裂荷载,进而由有限元计算得到其起裂断裂韧度值,分析了龄期变化对起裂断裂韧度的影响规律,给出了起裂断裂韧度随试件尺寸的变化规律。结果表明,通过现场浇筑试件,得到大坝混凝土的起裂断裂韧度,能够真实反映大坝的实际断裂性能。现场浇筑大坝混凝土的起裂断裂韧度随着龄期增加而增加,180 d龄期的现场浇筑大坝混凝土的起裂断裂韧度在试件有效高度800~1 200 mm范围内不存在明显的尺寸效应。
In this paper,the study aims to examine the initial fracture toughness KIinic of dam concrete obtained directly from a construction site. All test specimens with a maximum aggregate size of dmax = 150 mm were cast on site of an actual super-high arch dam in southwest China, and the dimensions of the wedge-splitting specimen were 800 mm×800 mm×450 mm,1000 mm×1000 mm×450 mm,1200 mm×1200 mm×450 mm, respectively. Based on the experimentally acquired initial cracking loads, the initial fracture toughness KI^inic of the site-casting specimens was numerically obtained using the finite element method. Furthermore,the effect of specimen age and size on initial fracture toughness was analyzed and discussed. The results show that real fracture parameter KI^inic of a super-high arch dam could be obtained by casting the test specimens at the construction site. The initial fracture toughness KI^inic of the site-casting specimens increases with specimen age. The KI^inic of the site-casting specimens at the age of 180 days is independent of specimen size at depths of 800 mm to 1200 mm.