Study on Acoustic Emission Characteristics and Instability Evolution Processes of Concrete Under Axial Compression

: The concrete of bridge pile foundations always bear excessive axial loads, and accompanying with its internal failure and crack process, elastic waves will be emitted. In order to quantify the characteristics of the entire instability evolution process of concrete, the temporal and spatial evolution characteristics of acoustic emission in the whole loading process of concrete specimens drilled in situ from bridge pile foundation structures were studied and synchronous monitoring tests of axial compression and acoustic emission were conducted. The relation between the whole process of compressive instability and the acoustic emission ringing counts, energy release, focal locations and other characterization parameters were analyzed. Then, a quantitative description of the correlation between the loading process and acoustic emission characteristics was obtained, and its instability evolution process was analyzed. The results indicated that the stress of concrete specimens under axial compression was consistent with the change law of the acoustic emission ringing counts and energy release with times, and the acoustic emission positioning points mainly located in a macro “positio-ning zone” in the shear stress concentration area, which was consistent with the development and failure of concrete cracks. The loading stage of concrete could be quantitatively judged according to activity of acoustic emission, which could reflected the critical characteristics of concrete instability, and was of great significance to service monitoring of pile foundation concrete.