Acoustic emission characteristics and fracture response behavior of hard rock-like material under influence of loading rate

For the purpose of clarifying the correlation between Acoustic Emission(AE) and rupture response characteristics and loading rate in the failure and instability of hard rocks, uniaxial compression tests and acoustic emission tests were conducted on hard rock-like material samples at different loading rates to analyze the characteristics of mechanical parameters, AE phenomena and rupture response characteristics of hard rock-like material, and to obtain the early warning information of the rock failure based on the information on AE parameters. The results show that the peak strength, elastic modulus and peak strain of hard rock-like material have the loading rate effect. The mechanical parameters generally increase exponentially with the increasing loading rate. The mechanical parameters grow rapidly at relatively low loading rates(0.10-0.15 kN/s), and are slightly slower at relatively high loading rates(0.20-0.25 kN/s). The AE parameters evolution shows a phased growth trend, and the maximum increase is positively correlated with the loading rate. As the loading rate increases, the AE amplitude and amplitude density gradually increase; the AE ringing counts change from low value-low frequency to high value-high frequency, and the AE energy from slone type to group type. The loading rate has a significant impact on rupture mode and fracture form. With the increase of the loading rate, the rock samples gradually evolve from shear failure to tensile-shear composite failure and tensile failure, and gradually shows an explosion tendency when the rupture degree increases. The b values of AE experience an evolution stage of first rising, then fluctuating and finally falling with the increase of the loading time, showing a gradual decreasing trend. The critical failure precursor(b value) is 0.68. The warning time sequence of AE precursor information is accumulated AE ringing counts, accumulated energy, b value from large to small, showing good timeliness and reliability. The research results provide a useful reference for revealing the mechanical characteristics and early warning of failure precursor information of hard surrounding rocks.