Abstract
In order to investigate the high loading rate effect on the behaviour and mechanical properties of coal-rock combined body, the dynamic compressive tests were conducted by using the Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×105 MPa/s to 4.0×105 MPa/s. The stress-strain curves, dynamic peak stress and strain, elastic modulus, and energy distribution law of coal-rock combined body under different loading rates were analyzed and discussed. The results show that the dynamic stress-strain curves of coal-rock combined body have a double-peak feature under high loading rate range, which can be divided into the initial bearing stage, the bearing decline stage, the bearing enhance stage, and the unstable stage. The first peak stress of the coal-rock combined body is independent of the loading rate, while the dynamic compressive strength (the second peak stress) and dynamic peak strain (the second peak strain) have a strong loading rate effect and will generally increase linearly with the loading rate. The first and second elastic moduli of coal-rock combined body are not sensitive to the loading rate. With the increase of the loading rate, the incident energy and reflective energy of coal-rock combined body increase rapidly, while the change of transmitted energy is very small. The absorption energy ratio of the coal-rock combined body shows a good linear law with the incident energy under different loading rates.
Highlights
In deep mining of coal mine, rock burst or coal burst is often encountered and is becoming more and more serious with the increase of depth, which seriously threatens the safety of mine production [1]
The dynamic compressive tests were conducted by using a Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×105 MPa/s to 4.0×105 MPa/s, and the strength characteristics, failure modes, and energy distribution law of coal-rock combined body were obtained and analyzed
It can be seen that the stresses on both ends of the coal-rock combined body specimen are very close, which indicates that the specimen will be in a state of stress equilibrium during the dynamic loading process
Summary
In deep mining of coal mine, rock burst or coal burst is often encountered and is becoming more and more serious with the increase of depth, which seriously threatens the safety of mine production [1]. Rock burst is essentially a dynamic failure of coal-rock combined body under the mining disturbance [2,3,4,5]. Zuo et al [6,7,8] studied the influence of dip angle, confining pressure, and different stress conditions on the failure characteristics of coal-rock combined body. The experimental research on coal-rock combined body under high loading rate was relatively few. The dynamic compressive tests were conducted by using a Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×105 MPa/s to 4.0×105 MPa/s, and the strength characteristics, failure modes, and energy distribution law of coal-rock combined body were obtained and analyzed
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