Source analysis of acoustic emissions during granite strain burst

Yang Wang^a,b, Manchao He^a, Fuqiang Rena^b, Chun Zhua^c and Lohrasb Faramarzi^d

^a State Key Laboratory for Geomechanics & Deep Underground Engineering, Beijing, China  

^b School of Mechanics and Civil Engineering, China University of Mining & Technology, Beijing, China  

^c College of Construction Engineering, Jilin University, Changchun, China  

^d Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran

Doi:10.1080/19475705.2019.1593888

ABSTRACT

The acoustic emission (AE) location technique and fault-plane solution method were used to evaluate the temporal-spatial evolution, released energy variation of micro-cracks, and the difference in b-values for different types of micro-cracks during granite strain burst tests. Results show that AE locations coincide with the macroscopic cracks in the ejection zone. AE locations are scattered for the fracture zone after unloading. The fragment ejection was the results of the combined action of shear, tensile, and compressional micro-cracks; furthermore, the released energy from compressional micro-cracks was largest at the moment of strain burst. Additionally, compressional micro-cracks were the most common, and the tensile micro-cracks were the lease common. For compressional micro-cracks, the overall trend of the b-values was downward, while b-values for shear and tensile micro-cracks both increased. For the fracture zones, the b-value of the microcracks was decreased firstly and then increased, while b-values for the ejection zones decreased firstly and then fluctuated and increased.

KEYWORDS: Fault-plane solution; AE location; event density; strain burst; b-value