Analysis of fracture behavior of full-graded dam concrete under variable loading rate based on acoustic emission and digital image correlation techniques

Three-point bending tests were conducted on full-graded dam concrete at variable loading rates in stages. The fracture damage process of the full-graded dam concrete during the variable loading rate was evaluated by the acoustic emission technique. At the same time, the strain field and displacement field of the fracture process of the full-graded dam concrete were analyzed by combining digital image processing techniques. The results show that: the peak load of concrete fracture increases with the increase of loading rate; in the late stage of the test loading stage, the loading rate increases, the acoustic emission signal becomes active significantly, the number of acoustic emission events increases significantly, and the slope of the cumulative acoustic emission event curve increases significantly; the increase of loading rate accelerates the crack development of the specimen, leading to the rapid development of a large number of microcracks into macro cracks, the damage extension of the specimen After the peak, the specimen enters the second stage, and the loading rate increases, the more rapidly the cracks develop, the larger the crack width, and the fracture damage of the specimen is more serious.