Study On The Characteristics Of Infrasound Signals Of Rock Failure Under Different Loading Paths

Rock failure process is a kind of energy is accumulated to a certain degree,and then suddenly release process,is a cumulative effect.So to carry out the monitoring of rock mass with physical phenomena in the process of energy accumulation and investigate its characteristics,for instability of rock mass damage precursor characteristics effect in the process of information,is the instability of rock mass can be monitoring and early warning research direction.Studies have shown that infrasound signal has the characteristics of transmission distance,small energy attenuation,overcome ambient infrasound noise interference,through the study of rock in the process of loading low frequency acoustic emission signal characteristic,establishing time correlation between sound signal and instability of rock mass,instability and failure of rock can be obtained important precursory information.In this paper,based on the indoor test The uniaxial compression test,shear test Brazilian split test and uniaxial cyclic unloading experiment four,for a variety of rock mechanics test and acoustic signal acquisition in time.The acquisition of infrasound signal wavelet decomposition and reconstruction,Get the 0 ~ 16 Hz infrasound time domain signal Analysis of infrasound time-domain signal characteristics,we get the following main conclusions:(1)By uniaxial compression test with the oblique shear test results analysis found that rock under variable shear failure forms can produce outstanding sound signals,and the final rock specimen stress peaks in the infrasound signal strength reached maximum.(2)In the process of fracturing infrasound signals with lab background difference is not big,acoustic signal is not obvious,splitting test infrasound phenomenon is not obvious there are two possible:the first,split the infrasound signal strength is less than the laboratory environmental noise infrasound signal strength;the second,the splitting test and destroyed most of the acoustic signal for high frequency signal,data processing has been filtered and infrasound signal is too little.(3)The test in the process of infrasound sensor and load of the rock sample interval linear distance is about 2.5 m space,obvious difference in acoustic emission monitoring sensors and rock sample tightly coupled way,that can sound signals generated by rock deformation and failure through the air,a certain distance sensors without direct contact with the rock mass and to monitor the stability of rock mass,which makes the field monitoring of the sound more convenient.(4)Through to the rock uniaxial cyclic and unloading experiments at various levels and uninstall the infrasound signal events accumulative ringing statistics,you can see that in the first category five and unloading phase(the peak stress is about 80% ~ 80% section)cumulative ringing count infrasound signal events during the unloading phase level significantly greater than the loading stage,abnormal.(5)The rock in the process of loading damage the infrasound signal of main frequency band energy distribution in1~4 Hz,stress in the initial stage1~4 Hz frequency band energy accounted for 50%,with the increasing of load stress and the frequency band energy proportion is more and more big,the peak point can reach more than 85%.(6)Fractal dimension in initial stages in a low stress,with the increase of load stress,the fractal dimension of volatility,began to appear big ups and downs in the initial stage,when the slump after the fractal dimension,signal impending rupture of rock.