Study On The Law Of Charge Induction And Microseismic Signals Of Coal And Rock Under Uniaxial Compression

The rock burst induced by sudden instability of coal and rock mass is a kind of sudden,random and violent engineering disaster.Warming timely of the disaster by monitoring the physical information which are caused by the instability of coal and rock mass and to take effective prevention and control will reduce consequences of accidents.Charge induction signals and microseismic signals are in great agreement with the stress abrupt of coal and rock mass.To monitor the stress evolutions of the coal and rock mass by combination with the charge induction and the microseismic system will improving the accuracy of the early warming effectively.Physical experiment is used by this paper as the main research method,established the monitoring system of charge and microseismic signals during coal-rock failure process,experimental studied on different loading rates,water content and multi-stage cycle loading,and analyzed the variation of charge and microseismic time domain signals and frequency domain signals.The result show:(1)The coal and rock are divided into four stages: compaction phase,elastic phase,strengthening phase and post-peak phase.The charge and microseismic time domain signals of coal and rock are discrete signals with short duration and concentrated distribution in the strengthening and post-peak phase.In the compaction and elastic phase,the relative amplitude of the main frequency of the microseismic signal increases first and then decreases,and the spectrum is evenly distributed in the wide frequency range.In the strengthening phase,the amplitude of the main frequency of the spectrum increases,and the spectrum shifts to the low frequency and has a high value.In the post-peak phase,the relative frequency of the main frequency gradually decreases,and the spectrum is concentrated in the low frequency but the high value decreases.(2)Under the cyclic loading,coal and rock dissipate internal energy to promote the development of cracks,charge induction and microseismic signals are more abundant than conventional uniaxial compression signals,and large amplitude signals appear earlier for the first time.(3)With the increase of the loading rate,the uniaxial compressive strength of the coal and rock mass increases,and the cumulative deformation energy consumption of the coal and rock mass increases.The time for the first significant charge and microseismic signal is advanced,and the subsequent quiet period is shortened.The large-amplitude charge induction signal in the strengthening phase transitions from burst to continuity,and the amplitude of the microseismic and charge signal spectrum increases,centralized distribution to low frequencies.(4)With the increase of water content,the uniaxial compressive strength of coal rock mass decreases,the post-peak softening phase of the specimengradually becomes obvious,the number of charge induction and microseismic signal events decreases.Based on the characteristics of charge and microseismic signal in time domain and the variation law of microseismic spectrum,preliminarily put forward the basis for determining the instability of coal and rock mass by charge and microseismic signal.This paper has 44 figures,2 tables and 76 references.