Detection of effects of rock burst prevention by water injection into coal seam using charge induction method

For detecting the effects of rock burst prevention by water injection into coal seam using the charge induction method, an experimental method is adopted to study the charge laws during the destruction process of coal samples with different moisture contents under uniaxial compression. The influences of water on the physical and mechanical properties of coal samples and the characteristics of the generated charge signals are analyzed. The charge induction method is used to monitor the process of water injection into coal seam. The change laws of charge signals and the principles of their production before, during and after water injection are analyzed. The results show that the presence of water weakens the friction between particles inside the coal samples and promotes the growth and development of micro porous cracks, causing water to weaken the production of charge signals. There is a phenomenon of stress drop without charge signal generation and hysteresis of charge signals. With the increase of moisture content, the average amplitude of charge of coal samples decreases exponentially. The relationship between the average amplitude of charge and the moisture content of coal samples is obtained, so the theoretical percentage of the charge drop corresponding to the increment of moisture content that meets the requirements of rock burst prevention in Gengcun coal mine is 50.13%. Therefore, the effects of rock burst prevention by water injection into coal seam can be evaluated according to the comparison between the actual and theoretical percentages of charge amplitude drop. The results of field monitoring show that charge amplitude is larger before and during water injection. The charge amplitude after water injection decreases by 52.65% compared with that before water injection, which is greater than the theoretical one of laboratory tests and meets the requirements of water injection into coal seam. Therefore, the charge induction method can be used to detect the effects of rock burst prevention by water injection into coal seam. However, a large number of laboratory and field tests are also required to correct and improve the proposed method continuously.