Acousctic Signal Characteristic Study Of Rockburst Process On Grantic

To date, Underground chambers are the main construction of large-scale Water Resources and Hydropower Engineering in the western of our country. During the excavation of these underground chambers, the rockburst has been taken as one of the increasingly striking hazards. Rockburst is a dynamic abrupt failure phenomenon caused by excavation in the rock mass with high geo-stress. As a consequence of the highly complex nature of rockburst, it is still one of the global hazards to predict the rockburst accurately in the depth. During the rockburst, acoustic wave with different frequency can be recorded. And the acoustic wave signal analysis can be one of the effective ways for rockburst prediction. Hence, the acoustic wave signal analysis during the rockburst process is capable of providing the scientific basis for establishing the rockburst prediction method based on acoustic signal, which has practical significance and academic value.In order to take a deep insight of the acoustic emission signal and perform a quantitative analysis of the rarely studied sound signal, rockburst process on granite rock sample were simulated successfully with the new-type true-triaxial rockburst test system in laboratory. The acoustic emission signal and sound signal were monitored during the whole tests. Based on the waveform analysis and frequency-spectrum analysis, the characteristics of the acoustic signal during the rockburst process were grained, and several conclusions can be obtained as follow:1、The hits, accumulative absolute energy and waveform parameter of the acoustic emission signal and waveform change characteristics of the sound signal can reflect the main phases of the rockburst. It should be noted that a period of low acoustic emission hits are similar to’quiescent period’before the eruption of the rockburst, which is corresponding to the’quiescent period’ of the waveform of the sound signal. In addition, during the period, the rise time and the duration time of the acoustic emission are all increased to the maximum.2、Both the acoustic emission hits and the sound signal waveform amplitude has the time-dependent factual features. The time-dependent factual demission can reflect the evolution process of the rockburst. Before the rockburst, these factual demission will increase to the maximum and then decline continuously within a period of time to the minimum.3、Different failure mode have different frequency-spectrum characteristics during the process of the rockburst. The frequency-spectrum characteristics of the acoustic emission signal during the loading stages of the tested rock sample including elastic-plastic, plastic and failure stages is similar to that of the sound signal, which is characterized by main frequency exhibiting the variation process of low frequency-high frequency-low frequency and frequency-spectrum showing repeated variation process of single peak type to multiple peak type. Before the rockburst, both acoustic emission signal and sound signal have the complex frequency complement. These acoustic signals have the characteristics of multiple main frequencies, multiple peak type frequency-spectrum and low amplitude to the main frequency.4、During the rockburst, the characteristic parameter, waveform parameter and frequency-spectrum of the acoustic emission signal as well as the waveform and the frequency-spectrum of the sound signal exhibit obviously features and specific evolution. Thus, both the acoustic emission signal and sound signal can be taken as the effective indicators of the rockburst. Furthermore, rockburst process can well be understood and predicted by combination of the acoustic emission signal and sound signal.