An EMR-based method for evaluating the effect of water jet cutting on pressure relief
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ORIGINAL PAPER
An EMR-based method for evaluating the effect of water jet cutting on pressure relief Dazhao Song & Enyuan Wang & Zhonghui Li & Enlai Zhao & Wenquan Xu
Received: 18 March 2014 / Accepted: 14 August 2014 # Saudi Society for Geosciences 2014
Abstract Water jet cutting (WJC) can play a good role in coal pressure relief. Its effect is commonly evaluated using a traditional method based on debris-drilling amount. However, this evaluating result is unsatisfactory due to great artificial interference. Based on previous experimental researches on the relationship of electromagnetic radiation (EMR) to stress during the failure of coal rock under loading, we analyze the EMR response to seam pressure relief using WJC from the angle of stress relief and carried out experiments to verify that EMR response could be used to evaluate the effect of WJC on coalbed pressure relief at Xinzhi and Yuejin Coal Mines, China, with self-developed KBD5 EMR monitor. The research showed that after WJC, the intensity and changes of EMR reflect not only the stress level from which the cut coal seam suffered but also the processes of stress transfer and evolution, thus proving that EMR can be used to evaluate the effect of WJC for coal mass pressure relief. Moreover, the experiments also showed that if without borehole collapse after WJC, multiple WJC in the same borehole can be performed to monitor EMR signals and when two adjacent signal curves keep at the same level and without obvious decline, WJC could fully release pressure in coal mass. D. Song : E. Wang : Z. Li : E. Zhao School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China D. Song (*) Postdoctoral Research Station, Yongcheng Coal & Electricity Holding Group Co. Ltd, Yongcheng 476600, China e-mail: [email protected] E. Wang Key Laboratory of Gas and Fire Control for Coal Mines, Xuzhou 221008, China W. Xu Coal Mining Technology Department, Shaanxi Coal and Chemical Technology Institute Co., Ltd, Xi’an 710065, China
Keywords Water jet cutting . Electromagnetic radiation . Pressure relief . Evaluation method . Coal rock
Introduction Water jet cutting technology (WJCT) has been investigated theoretically and practically by many scholars. When directed to hard materials such as coal, rock, and the like, a high pressure water jet can change their original states and structures in a controllable manner (Farmer and Attewell 1965; Daniel 1976; Vjay et al. 1984; Fenn 1989; Momber and Kovacevic 1997 and Kang et al. 2012). For the underground coal seams subjected to great stress, WJC can locally destroy them and play a good role in pressure relief. Moreover, water media applications not only avoid producing static sparks but also prohibit or precipitate coal dust. Thus, WJCT has been widely used in the prevention of coal mine dynamic disasters. Scholars have theoretically and experimentally investigated the effects of WJC in underground working faces. Lin et al. (2011) found through numerical simulations that the cut depth with a high pres
