Abstract
The acoustic emission (AE) and ultrasonic (UT) simultaneous monitoring program is designed using concrete samples under step loading. The time‐varying response characteristics of AE‐UT are studied and the cross‐correlation analysis between AE‐UT parameters is obtained. Moreover, the joint response of UT‐AE spatial distribution field is analyzed, and an AE‐UT joint monitoring method to detect early‐warning signals of a rockburst disaster in a coal seam is proposed. The results show the following. (1) During the loading process, the AE pulses/energy and UT attenuation coefficient first slowly decrease and then increase steadily and finally rapidly increase, while the UT velocity shows a trend of first gradually increasing and then slowly decreasing and finally a sharp decline. (2) AE pulses and energy are significantly or highly correlated with the UT velocity and attenuation coefficient. The AE energy and UT attenuation coefficient can better characterize the damage evolution of concrete under step loading. (3) The UT field evolves ahead of the rupture on the surface, and the long/narrow strip distribution region of UT parameters is consistent with the future failure zone; meanwhile, the AE events can visually reflect the evolution path of internal damage as well as the dynamic migration mechanism of UT field.
Highlights
Concrete as a raw material is widely used in construction engineering such as buildings, roadways, bridges, and tunnels
There must be a certain correlation between UT and acoustic emission (AE) parameters
We propose using the AE-UT joint monitoring method to forecast the rockburst disasters in the longwall working face
Summary
Concrete as a raw material is widely used in construction engineering such as buildings, roadways, bridges, and tunnels It is very important for public safety to carry out damage analysis, stability monitoring, and remaining life estimation of those constructions using appropriate methods [1]. Stress/strain under the failure process of brittle rocks and found the critical point of wave velocity to predict the geological hazards based on Weibull’s distribution and renormalization group theory. All of these researches show that the UT parameters have a close relationship with the applied stress, and the closure, initiation, propagation, and coalescence processes of internal cracks are the basic reasons for the change of UT parameters. The research results can provide an important experimental basis for damage estimation, instability disasters early warning, and a better understanding of the damage evolution mechanism comprehensively
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