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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。
Using the concrete mixing floor at the construction site of a special high arch dam in the southwestern part of China, the dam concrete wedged to form the largest aggregate with a diameter of 150 mm was wedged into the splitting tensile specimens with dimensions of 800 mm × 800 mm × 450 mm, 1 000 mm × 1000 mm × 450 mm and 1 200 mm × 1 200 mm × 450 mm. Through the test, the initiation load of dam concrete specimens cast in situ was obtained, and then the fracture toughness values of the concrete specimens were calculated by finite element method. The influence of age on the fracture toughness of fracture initiation was analyzed. The toughness changes with the size of the specimen. The results show that the fracture toughness of the dam concrete can be obtained by pouring the specimen on site, which can truly reflect the actual fracture performance of the dam. The fracture toughness of concrete pouring at site increased with the increase of age. The fracture toughness of initial pouring of concrete at 180 days was not obvious at the effective height of 800-1 200 mm The size effect.