An Experimental Investigation into the Strainburst Process Under Quasi-static Loading
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ORIGINAL PAPER
An Experimental Investigation into the Strainburst Process Under Quasi‑static Loading Fuqiang Gao1,2 · Hongpu Kang1,2 · Lei Yang1,2 Received: 2 March 2020 / Accepted: 17 August 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Rockbursts cause damage to underground excavations in a sudden and violent manner and are associated with mining-induced seismic events. We propose a simple experimental method to study strainburst process in the laboratory, that simply involves a common compression testing apparatus and rock-coal-rock specimens. Strainbursts of coal samples are successfully produced and the burst process is monitored using high-speed camera and acoustic emission sensors. The strainburst mechanism is characterized by an initial ejection of small coal fragments followed by the ejection of large coal blocks. We found that the strainbursts are caused by the elastic strain energy stored in the rock samples during the uniaxial compression. The amount of the transferred energy is significantly less than the elastic energy stored in the coal sample but plays an important role in triggering strainbursts. The greater the transferred energy, the greater the damage severity of strainbursts occurred in the coal sample. Tensile cracking subparallel to the vertical loading direction and tangential compressive stress appears to play a dominant role in the strainburst failure mechanism. Keywords Strainbursts · Dynamic failure · Elastic strain energy · Laboratory test
1 Introduction Rockbursts are violent excavation-induced events that involve the sudden failure and, if ineffectively supported, the ejection of rock from the surface of an underground excavation. Rockbursts can cause fatalities and/or injuries to workers, damage mine/civil infrastructure and/or equipment and disrupt production. Rockburst hazards increase with deeper mining and civil tunnelling operations and present serious operational and safety challenges. During a rock burst, rock particles can be ejected with a velocity of 8–50 m/s, which can inflict fatal injuries and damage underground equipment (Ortlepp 1993). Rockbursts can be classified based on different failure mechanisms: strainbursts, pillar bursts, and fault-slip bursts (Kaiser et al. 1996; Kaiser and Cai 2012; Cai and Kaiser 2018). Strainbursts are likely the most common type and generally occur when
* Fuqiang Gao [email protected] 1
CCTEG Coal Mining Research Institute, Beijing, China
State Key Laboratory of Coal Mining and Clean Utilization (China Coal Research Institute), Beijing, China
2
stresses near the excavation boundary reach the rock mass strength. Despite tremendous efforts devoted to understanding strainburst mechanisms, significant challenges remain in the assessment and management of rockburst hazards towing mostly to complex and uncertain geological conditions, in-situ stresses, induced stresses (relative to the presence of localised stress heterogeneity), and triggering conditions. Many experimental studies have attempted to
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