• PDF / 4,126,081 Bytes
• 17 Pages / 547.087 x 737.008 pts Page_size
• 33 Downloads / 235 Views

DOWNLOAD

REPORT

---

Pure and Applied Geophysics

Study on Loading Rate Dependence of the Coal Failure Process Based on Uniaxial Compression Test WEIJING XIAO,1,2

DONGMING ZHANG,1,2 YING CAI,3 and YAPEI CHU1,2

Abstract—To study the influence of the loading rate on the failure process of coal, uniaxial compression tests were performed with various axial strain rates of 0.83 9 10–5 to 6.66 9 10–5 s-1 on coal samples, which were collected from the Shamushu Coal Mine in Sichuan Province. The parameters of stress, strain, and acoustic emission during the failure process were collected and recorded. The peak stress, axial strain stiffness, energy dissipation, and acoustic emission characteristics of coal samples with different axial strain rates were analysed. The results demonstrate that (1) as axial strain rates increase, the peak strength and degree of fragmentation of the coal sample after failure also increase, and they exhibit good dependence on the axial strain rate; (2) the axial strain rate has little influence on the change trend in strain stiffness during the process of failure, but as the axial strain rate increases, the strain stiffness value of the horizontal section of the axial strain stiffness curve increases, and the initial stress level of this stage has a forward trend; (3) as the axial strain rate increases, the total energy absorbed by the coal sample increases gradually, and the proportion of elastic strain energy decreases when the peak stress is reached, while the proportion of dissipated energy increases gradually; (4) as the axial strain rate increases, the AE signal’s activity increases in the process of sample failure, the threshold value of the strain level decreases corresponding to AE active and intense periods, and higher amplitude AE signals are produced in the violent period. The research results can provide reference for monitoring and controlling geological hazards, such as pillar instability and failure in underground mining. Keywords: Uniaxial compression, rock mechanics, axial strain rate, energy dissipation, acoustic emission.

1 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China. E-mail: [email protected] 2 School of Resources and Safety, Chongqing University, Chongqing 400044, China. 3 School of Civil Engineering, Chongqing University, Chongqing 400044, China.

1. Introduction Deep mining of resources has led the geological environment of underground mine working areas to become more complex and varied (Qiu et al. 2014; Wang et al. 2009; Li et al. 2016). Large-scale mining changes the stress and seepage fields of stratum structures, and the forms of instability and failure are becoming increasingly complicated (Liu et al. 2019; Chao et al. 2019, 2020). Dynamic disasters, such as mine earthquakes and rock bursts, have become key, urgent problems in the field of coal mining (Li and Liu 2011; Wang et al. 2013a, b, 2014). In the process of underground mining, the ore pillar is permanently preserved as an important engineering rock mass, which