A new experimental apparatus for sudden unloading of gas-bearing coal

  • Gang WangEmail author
  • Yangyang Guo
  • Pengfei Wang
  • Wenxin Li
  • Mengmeng Wu
  • Lulu Sun
  • Jianjun Cao
  • Changang Du
Original Paper


To study the characteristics of the deformation and failure of coal during a coal and gas outburst, we developed an experimental apparatus that subjected coal samples to sudden unloading under various gas conditions. The apparatus consisted of a coal sample cell, a fast pressure unloading system, a monitoring and control system, and a gas filling system. The gas filling system was equipped with safe, explosion-proof solenoid valves for gas pressure unloading and an accurate strain chip for measuring sample strain. The apparatus was designed to probe the influence of the gas on coal and gas outbursts. The study focused on the mechanism by which high-pressure gas influences coal and gas outbursts, leading to the deformation characteristics of the sudden unloading process. The experimental results showed that the plastic deformation of coal samples in the presence of methane gas can be divided into three stages: compression induced by increased pressure, expansion induced by adsorption, and deformation or failure induced by sudden unloading. The results of tests performed in the presence of helium revealed that the deformation could be divided into just two stages: a compression stage induced by increased pressure and a recovery stage induced by sudden pressure unloading. Coal samples were found to deform much more rapidly and to a greater degree in methane than in helium, and the expansive deformation and failure of the coal sample become increasingly apparent with increasing initial gas pressure. Overall, our results demonstrate that the experimental apparatus developed here provides a feasible means to test the characteristics of the coal damage and gas migration that occur during a coal and gas outburst.


Coal and gas outburst Sudden pressure unloading Gas pressure Deformation Gas type 



The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (project no. 51674158; project no. 51704187), the Source Innovation Program (Applied Research Special-Youth Special) of Qingdao (project no. 17-1-1-38-jch), the Shandong University of Science and Technology Research Fund (project no. 2015JQJH105), and the Taishan Scholar Talent Team Support Plan for Advantaged & Unique Discipline Areas.


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Copyright information

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Authors and Affiliations

  1. 1.Mine Disaster Prevention and Control—Ministry of State Key Laboratory Breeding BaseShandong University of Science and TechnologyQingdaoPeople’s Republic of China
  2. 2.College of Mining and Safety EngineeringShandong University of Science and TechnologyQingdaoPeople’s Republic of China
  3. 3.College of Mining and Safety EngineeringShandong University of Science and TechnologyQingdaoPeople’s Republic of China
  4. 4.Department of Civil and Architectural EngineeringCity University of Hong KongHong KongChina
  5. 5.China Coal Technology Engineering Group Chongqing Research InstituteChong QingChina

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