Strainburst process of marble in tunnel-excavation-induced stress path considering intermediate principal stress
Tunnel excavation stress path considering the influence of intermediate principal stress
Experimental study on the process of marble strain rock burst
Bangyou Jiang , Shitan Gu , Lianguo Wang , Guangchao Zhang & Wenshuai Li
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Rock burst is a kind of rock dynamic failure phenomenon which often occurs in the process of deep tunnel excavation. Generally, it can be divided into three types: strain rock burst, fault slip rock burst and rock pillar rock burst. Strain rock burst is the most common type of rock burst, which usually occurs near the excavation boundary of tunnel. It is caused by the local high stress concentration and the instantaneous release of elastic strain energy during the excavation process, often resulting in heavy casualties and economic losses, which has attracted the attention of scholars at home and abroad.
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Professor Gu Shitan's research group of energy and Mining Engineering College of Shandong University of science and technology and Professor Wang Lianguo's research group of State Key Laboratory of deep geomechanics and underground engineering of China University of mining and technology jointly carried out the experimental research on marble strain rockburst process under the tunnel excavation stress path considering the influence of intermediate principal stress. Two test paths are designed, one is the commonly used true triaxial unloading rockburst test path (Figure 1a), the other is a new test path considering the change of the main stress in the middle of the surrounding rock during the tunnel excavation process (Figure 1b).
(a) Stress path a
(b) Stress path B (considering σ 2 Variation)
Fig. 1 two stress paths of strain rock burst test
The test results show that: under the two test paths, the marble rock samples have undergone the phenomenon of stress-strain rock burst, but the process of rock sample stress-strain rock burst is more intense when considering the change of the intermediate principal stress. With the increase of the peak value of the intermediate principal stress σ 2A before unloading, the failure of the unloading surface of the specimen gradually changes from slight ejection and stripping failure to severe ejection failure (Fig. 2). This is because when the higher intermediate principal stress σ 2 acts on the specimen before unloading, more elastic strain energy can be released in the specimen, and the failure process must be more intense.
(a) Stress path a
(b) Stress path B
Fig. 2 process of rock burst under two stress paths
At the same time, it is revealed that the larger the peak value σ 2a of the intermediate principal stress before unloading, the more elastic strain energy accumulated in the rock sample and the greater the accumulated acoustic emission energy during the failure process, that is, the more elastic strain energy released during the failure of the rock sample, the larger the total mass and the larger the particle size of the ejected debris when the rock burst failure occurs, as shown in Figure 3. When the peak value of the intermediate principal stress σ 2A increases from 60MPa to 75mpa before unloading, the total mass of the ejected debris increases by 3.87%, and the cumulative acoustic emission energy increases by 15.9%.
Fig. 3 Variation of cumulative AE energy and total mass of ejected debris with the peak value of intermediate principal stress σ 2A before unloading
The research results recently published in Journal of Central South University are of great significance to reveal the rock burst mechanism under the stress path of tunnel excavation. The first author of this paper is Jiang BANGYOU, lecturer of energy and Mining Engineering College of Shandong University of science and technology.
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Author introduction
Jiang BANGYOU, male, born in July 1989, Ph.D., lecturer, master's supervisor, graduated from China University of mining and technology in 2017 with a Ph.D. in engineering mechanics. He is mainly engaged in the teaching and research work of mine rock mechanics, rockburst / rockburst mechanism and prevention and control. His research achievements have won one second prize of science and technology progress of Chinese society of rock mechanics and engineering, 10 national invention patents and 12 SCI / EI journal papers.
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Journal of Central South University Journal of Central South University (English version) is an English science and technology journal sponsored by the Ministry of education. It mainly reports the cutting-edge research results of materials, mineral processing, metallurgy, chemical industry, electromechanical, information, environment, transportation, geology, mining, civil engineering and other professional disciplines. It has been SCI, EI, Scopus, statistical source of Chinese scientific and technological papers, citation database of Chinese scientific papers, etc It is included in well-known databases at home and abroad. In 2019, it won the project support of "China Science and technology journal excellent action plan".
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