Investigation of the discharge law for drill cuttings used for coal outburst prediction based on different borehole diameters under various side stresses

Cheng Zhai, Jizhao Xu, Shimin Liu, Lei Qin

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Prediction is the first step to prevent and control coal outburst geological disasters. Generally, both limits and disadvantages are generated for the traditional prediction methods of drill cuttings from a Φ42 mm borehole with increased mining depths. To investigate the discharge law of drill cuttings and improve the prediction index, briquettes were drilled with different borehole diameters under various side stresses. All the briquettes were loaded by a tri-axial experimental system to simulate the side stress of coal rock, and acoustic emission (AE) was used to monitor the AE events and record their characteristics during the separate drilling processes. The results showed that a larger borehole diameter and higher surrounding rock stress caused an increase in the quantity of drill cuttings (S). A power function relationship between S and the borehole diameter was found under the same side stress, and S was positively correlated to the side stress of a certain borehole diameter. Incremental drill cutting quantity (ΔS) was proposed to be the prediction index and the relationship between ΔS and the borehole diameter was fitted as a power function with a fitting coefficient of more than 0.99. The coupled values of ΔS and AE energies measured from a Φ85 mm borehole were more sensitive than those of a Φ35 mm borehole. In addition, the peak stress area using the larger drill bit was delayed by approximately 40 mm compared to that of the Φ35 mm drill bit. Larger diameter boreholes are preferable for larger regions of stress-relief and outburst removal; as a result, the use of larger diameter boreholes provides technological support to improve mine safety and increase production efficiency.

Original languageEnglish (US)
Pages (from-to)396-404
Number of pages9
JournalPowder Technology
Volume325
DOIs
StatePublished - Feb 1 2018

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)

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