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Geomechanics and Engineering
  Volume 15, Number 5, August10 2018 , pages 1113-1124
DOI: https://doi.org/10.12989/gae.2018.15.5.1113
 


Strength and failure characteristics of the rock-coal combined body with single joint in coal
Da W. Yin, Shao J. Chen, Bing Chen, Xing Q. Liu and Hong F. Ma

 
Abstract
    Geological dynamic hazards during deep coal mining are caused by the failure of a composite system consisting of the rock and coal layers, whereas the joint in coal affects the stability of the composite system. In this paper, the compression test simulations for the rock-coal combined body with single joint in coal were conducted using PFC2D software and especially the effects of joint length and joint angle on strength and failure characteristics in a rock-coal combined body were analyzed. The joint length and joint angle exhibit a deterioration effect on the strength and affect the failure modes. The deterioration effect of joint length of L on the strength can be neglected with a tiny variation at alpha of 0o or 90o between the loading direction and joint direction. While, the deterioration effect of L on strength are relatively large at alpha between 30o and 60o. And the peak stress and peak strain decrease with the increase of L. Additionally, the deterioration effect of alpha on the strength becomes larger with the increase of L. With the increase of alpha, the peak stress and peak strain first decrease and then increase, presenting \"V-shaped\" curves. And the peak stress and peak strain at alpha of 45o are the smallest. Moreover, the failure mainly occurs within the coal and no apparent failure is observed for rock. At alpha between 30o and 60o, the secondary shear cracks generated in or close to the joint tips, cause the structural instability failure of the combined body. Therefore, their failure models present as a shear failure along partial joint plane direction and partially cutting across the coal body or a shear failure along the joint plane direction. However, at alpha of 60o and L of 10 mm, the \"V-shaped\" shear cracks cutting across the coal body cause its final failure. While crack nucleations at alpha of 0o or 90o are randomly distributed in the coal, the failure mode shows a V-shaped shear failure cutting across the coal body.
 
Key Words
    particle flow simulation; strength and failure characteristics; rock-coal combined body; single joint in coal; joint length and joint angle
 
Address
Da W. Yin and Shao J. Chen: 1.) College of Mining and Safety Engineering, Shandong University of Science and Technology, 579 Qianwanggang Road, Huangdao District, Qingdao, Shandong Province, 266590, China
2.) Key Laboratory of Safety and High-efficiency Coal Mining, Ministry of Education, Anhui University of Science and Technology, Huainan 232001, China

Bing Chen, Xing Q. Liu and Hong F. Ma: College of Mining and Safety Engineering, Shandong University of Science and Technology, 579 Qianwanggang Road, Huangdao District, Qingdao, Shandong Province, 266590, China
 

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