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Geomechanics and Engineering
  Volume 22, Number 5, September10 2020 , pages 385-396
DOI: https://doi.org/10.12989/gae.2020.22.5.385
 


Mechanical properties and failure mechanisms of sandstone with pyrite concretions under uniaxial compression
Shao J. Chen, Meng Z. Ren, Feng Wang, Da W. Yin and Deng H. Chen

 
Abstract
    A uniaxial compression test was performed to analyse the mechanical properties and macroscale and mesoscale failure mechanisms of sandstone with pyrite concretions. The effect of the pyrite concretions on the evolution of macroscale cracks in the sandstone was further investigated through numerical simulations with Particle Flow Code in 2D (PFC2D). The results revealed that pyrite concretions substantially influence the mechanical properties and macroscale and mesoscale failure characteristics of sandstone. During the initial loading stage, significant stress concentrations occurred around the edges of the pyrite concretion accompanied by the preferential generation of cracks. Meanwhile, the events and cumulative energy counts of the acoustic emission (AE) signal increased rapidly because of friction sliding between the concretion and sandstone matrix. As the axial stress increased, the degree of the stress concentration remained relatively unchanged around the edges of the concretions. The cracks continued growing rapidly around the edges of the concretions and gradually expanded toward the centre of the sample. During this stage, the AE events and cumulative energy counts increased quite slowly. As the axial stress approached the peak strength of the sandstone, the cracks that developed around the edges of the concretion started to merge with cracks that propagated at the top-left and bottom-right corners of the sample. This crack evolution ultimately resulted in the shear failure of the sandstone sample around the edges of the pyrite concretions.
 
Key Words
    pyrite concretion; mechanical properties; failure mechanics; acoustic emission; discrete element method
 
Address
Shao J. Chen, Meng Z. Ren and Da W. Yin: College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China

Feng Wang: 1.) College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
2.) Key Laboratory of Safety and High-efficiency Coal Mining, Ministry of Education,
Anhui University of Science and Technology, Huainan, Anhui 232001, China

Deng H. Chen: Key Laboratory of Safety and High-efficiency Coal Mining, Ministry of Education, Anhui University of Science and Technology, Huainan, Anhui 232001, China
 

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