Nakamura Spectral Ratio Characteristics of Microseism Signal Induced by Relieve-Shot.

Abstract: By weakening the strength of coal-rock masses and releasing large elastic energy accumulated, relieve-shot can reduce the rockburst tendency. The accurate assessment of the relieve-shot effect has an important guiding significance for dynamic prevention of rockburst. Based on the basic supposition of Nakamura method, Nakamura spectral ratio model of microseismic (MS) signal propagation of relieve-shot was effectively established. The Nakamura spectral ratio can reveal the predominant resonance frequency evolution rule of coal-rock mass after relieve-shot being discovered. Through the relieve-shots implemented in 7206 driving working face of Sanhejian coal mine (SCM), Nakamura spectral ratios of relieve-shot MS signals were analyzed in detail. The bigger Nakamura spectral ratio is, the higher the stress in coal and rock materials is. High dominant frequency of Nakamura spectrum ratio indicates loose and cracked rock and coal mass where elastic energy is released effectively, thereby high resonant frequency can be created, which suggests the effect of pressure release blasting is desirable. Meanwhile, another relieve-shot effect is effectively checked by measuring drilling bits on spot. Therefore, the correlation between Nakamura spectral ratio and MS signal predominant frequency can evaluate the relieve-shot effect more accurately. [Copyright &y& Elsevier]