Effect of initial minimum principal stress and unloading rate on the spalling and rockburst of marble: a true triaxial e
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ORIGINAL PAPER
Effect of initial minimum principal stress and unloading rate on the spalling and rockburst of marble: a true triaxial experiment investigation Quan Jiang 1 & Meizhu Zhang 1,2,3 & Fei Yan 1
&
Guoshao Su 4 & Xiating Feng 1 & Dingping Xu 1 & Guangliang Feng 1
Received: 15 September 2019 / Accepted: 30 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Hard rock often performs as brittle failures, such as cracking, spalling, and rockburst, induced by excavation in deep underground engineering. To understand the effect of the minimum principal stress and unloading rate on the spalling and rockburst of marble, unloading experiments were carried out by using true triaxial equipment combined with a high-speed camera, acoustic emission instrumentation, and scanning electron microscope. The experimental results showed that the failure process of marble specimens was more stable and less inclined to exhibit dynamic ejection with a low strain energy release per unit time under a low unloading rate. At the same time, the initial minimum principal stress controlled the marble’s failure mode by changing its mode from predominantly shear failure to shear-tension failure as the minimum principal stress decreased, similar to the spalling behaviors of surrounding rock observed in the underground tunnel. What’s more, the dynamic rockburst of the marble specimen was simulated under the condition with a high unloading rate, high initial minimum principal, and free face on the specimen. Based on these experimental investigations, a flowchart was also presented to estimate the possible failure mode of marble specimens under different initial minimum principal stress and unloading rate conditions, which would be conducive to the disaster prevention of hard rock in deep underground engineering. Keywords Rockburst . Spalling . Unloading rate . Minimum principal stress . Tensile failure
Introduction Excavation of deep underground tunnel changes the initial equilibrium of the hard rock and inevitably causes intensive stress redistribution and local accumulation of elastic strain energy (Bandis et al. 1989; Kaiser et al. 2001; Martin et al. 2003; Diederichs et al. 2004; Wu et al. 2017). The unstable stress condition and energy accumulation frequently result in
* Fei Yan [email protected] 1
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
Uppsala University, 256, SE-751 05 Uppsala, Sweden
4
Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, School of Civil and Architecture Engineering, Guangxi University, Nanning 530004, China
unpredictable disasters characterized by static brittle failure, such as cracking and spalling (Fairhurst and Cook 1966; Harrison and Hudson 2010), or dynamic brittle failure, i.e., rockburst (Ortlepp and Stacey 1994; Jiang et al. 2010; He et al. 2014; Da
