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Geomechanics and Engineering
  Volume 14, Number 5, April10 2018, pages 459-466

Dilatation characteristics of the coals with outburst proneness under cyclic loading conditions and the relevant applications
Yangyang Li, Shichuan Zhang and Baoliang Zhang

    By conducting uniaxial loading cycle tests on the coal rock with outburst proneness, the dilatation characteristics at different loading rates were investigated. Under uniaxial loading and unloading, the lateral deformation of coal rock increased obviously before failure, leading to coal dilatation. Moreover, the post-unloading recovery of the lateral deformation was rather small, suggesting the onset of an accelerated failure. As the loading rate increased further, the ratio of the stress at the dilatation critical point to peak-intensity increased gradually, and the pre-peak volumetric deformation decreased with more severe post-peak damage. Based on the laboratory test results, the lateral deformation of the coals at different depths in the #1302 isolated coal pillars, Yangcheng Coal Mine, was monitored using wall rock displacement meter. The field monitoring result indicates that the coal lateral displacement went through various distinct stages: the lateral displacement of the coals at the depth of 2-6 m went through an \"initial increase-stabilize-step up-plateau\" series. When the coal wall of the working face was 24-18 m away from the measuring point, the coals in this region entered the accelerated failure stage; as the working face continued advancing, the lateraldisplacement of the coals at the depth over 6 m increased steadily, i.e., the coals in this region were in the stable failure stage.
Key Words
    rock mechanics; different loading rates; stress-strain curve; coal dilatation; lateral deformation
Yangyang Li and Shichuan Zhang: State Key Laboratory of Mining Disaster Prevention and Control, Shandong University of Science and Technology, Shandong 266590, China

Baoliang Zhang: College of Architecture Engineering, Liaocheng University, Shandong 252000, China

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