Rock Mechanics and Rock Engineering

, Volume 47, Issue 2, pp 467–483 | Cite as

Influence of Unloading Rate on the Strainburst Characteristics of Beishan Granite Under True-Triaxial Unloading Conditions

  • X. G. Zhao
  • J. Wang
  • M. Cai
  • C. Cheng
  • L. K. Ma
  • R. Su
  • F. Zhao
  • D. J. Li
Original Paper


Rockburst is a sudden and violent failure of rocks and it often occurs in hard rocks in highly stressed ground. Strainburst is classified as one type of rockburst and it often occurs in rocks near or at the excavation boundary. Deep insight into the strainburst phenomenon is essential for safe underground construction at depth. In this paper, an experimental laboratory study on the strainburst behavior of Beishan granite is presented. Based on in-situ stress measurement data from the Beishan area in China, a series of tests under different unloading rates were performed to investigate the strainburst process using a true-triaxial strainburst test system which was equipped with an acoustic emission (AE) monitoring system. In addition, a high-speed video camera was used to record and visualize the initiation and ejection of rock fragments as well as the sudden dynamic failure (strainburst) of the test samples. AE characteristics associated with the cumulative energy and frequency–amplitude distributions were analyzed. Characteristics of the microscopic structure of a fragment generated from one test were observed using a scanning electron microscope. The experimental results indicate that the degree of violence during failure and the associated AE energy release in the strainburst process are dependent on the unloading rate. When the unloading rate is high, the rock is prone to strainburst. On the other hand, as the unloading rate decreases, the failure mode changes from strainburst to spalling. In addition, the cumulative AE energy is not sensitive to unloading rates greater than 0.05 MPa/s. When the unloading rate is less than 0.05 MPa/s, the cumulative AE energy shows a marked decreasing trend during rock failure.


Rockburst Strainburst Stress path Unloading rate Acoustic emission Beishan granite 



This work has been supported by the China Atomic Energy Authority through the geological disposal program and the National Natural Science Foundation of China (Grant no. 11102061). Financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada is also appreciated. The authors thank Prof. M. C. He for his help and meaningful discussions on the strainburst tests, and Dr. S. Yong for reviewing the English of the manuscript. The authors also thank the two anonymous reviewers for their valuable comments and suggestions.


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Copyright information

© Springer-Verlag Wien 2013

Authors and Affiliations

  • X. G. Zhao
    • 1
  • J. Wang
    • 1
  • M. Cai
    • 2
  • C. Cheng
    • 3
    • 4
  • L. K. Ma
    • 1
  • R. Su
    • 1
  • F. Zhao
    • 3
    • 4
  • D. J. Li
    • 3
    • 4
  1. 1.CNNC Key Laboratory on Geological Disposal of High-level Radioactive WasteBeijing Research Institute of Uranium GeologyBeijingChina
  2. 2.Bharti School of EngineeringLaurentian UniversitySudburyCanada
  3. 3.State Key Laboratory for GeoMechanics and Deep Underground EngineeringBeijingChina
  4. 4.School of Mechanics, Architecture and Civil EngineeringChina University of Mining and TechnologyBeijingChina

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