Fracture Properties of Full-Graded Dam Concrete under Discontinuous Cyclic Loading Based on Acoustic Emission

Abstract

Concrete dams are often subjected to complex loading conditions throughout their operational lifespan. This study investigates the fracture behavior of full-graded dam concrete (FGDC) under the combined action of cyclic and static loads, utilizing discontinuous cyclic fracture tests (DCFTs). With respect to static load, loading intervals with different duration and force are considered. Moreover, the acoustic emission (AE) technique is employed to monitor the fracture process in real time. The experimental results reveal a three-stage characteristic in the evolution of the maximum crack mouth opening displacement (CMOD) for both continuous cyclic fracture tests (CCFTs) and DCFTs. Furthermore, the total number of cyclic circles in DCFTs is smaller than that of CCFTs. The AE technique effectively characterizes the fracture process, and the cracking behavior is analyzed based on the rise angle (RA), average frequency (AF), AE amplitude, and location. The b value, calculated as the slope of the frequency-magnitude log-line, is also utilized to analyze the cracking behavior. The variations in b value reflect the information from the initiation of microcracks to the formation of macrofractures. The crack types are successfully classified using unsupervised machine learning methods of the Gaussian mixture model (GMM), and the self-organizing map (SOM). Finally, the width of the fracture process zone is determined, and a larger value of width in DCFTs is found.