Affiliation:
1. College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, China
2. State Key Laboratory of Coal Resources and Safe Mining, School of Mines, China University of Mining and Technology, Xuzhou 221116, China
Abstract
To reveal the influence mechanism of mining speed on roof fracture-type rockburst, the Brazilian split technique combined with acoustic emission monitoring technology was employed to study the effects of loading rates on the tensile failure characteristics and acoustic emission parameters of coal series sandstone. The linear relationship between the tensile strength of the samples and the change rate of tensile stress was determined. The mining speed was introduced into the mechanical model of initial and cyclic fracture of the hard roof, and the quantitative relationship between the maximum rate of change of tensile stress within the hard roof and the mining speed was derived. Based on this, a computational model for the bending elastic energy of the hard roof during initial and cyclic fractures, considering the mining speed, was established. The main findings are as follows: As the loading rate increases, the distribution range of acoustic emission energy in sandstone Brazilian split samples before failure widens, with a significant rise in acoustic emission ring-down counts and energy at failure. At lower loading rates, acoustic emission events primarily occur near sample failure, whereas at higher rates, they mostly happen in the early loading stage. The higher the mining speed, the less opportunity there is for internal micro-fractures to develop and expand before the hard roof fractures, which macroscopically results in increased tensile strength and a larger amount of energy released at the moment of fracture. Bending elastic energy rises approximately linearly with mining speed, and the thicker the hard roof, the more sensitive the bending elastic energy is to changes in mining speed. This effect is even more pronounced during cyclic fractures. Optimizing mining speed is crucial for preventing roof fracture-type rockbursts, especially in mining workfaces with thick and hard roofs.
Funder
National Natural Science Foundation of China
China National Natural Science Foundation Youth Funding Project
Reference32 articles.
1. Theoretical basis and key technology of prevention and control of coal-rock dynamic disasters in deep coal mining;Qi;J. China Coal Soc.,2020
2. Advancing rate effect on rock and coal failure format in highintensity mining face;Yang;J. China Coal Soc.,2016
3. The effect of loading rate on the compressive and tensile strength of rocks;Wu;Chin. J. Geotech. Eng.,1982
4. Direct tension test for rock material under different strain rates at quasi-static loads;Li;Rock Mech. Rock Eng.,2013
5. Research on loading rate effect of tensile strength property of hard brittle marble—Test characteristics and mechanism;Zhou;Chin. J. Rock Mech. Eng.,2013