Study On Stress Wave Spectrum And Frequency Band Energy Characteristics Of Red Sandstone With Axial Static Load

The static load such as the self weight stress and tectonic stress has already been carried out when rock mass is subjected to dynamic loading such as drilling and blasting.Therefore,it is concluded that the stress wave propagation in the actual engineering rock mass can be induced by a certain static stress.The red sandstone of Ganzhou prepared for cross section of long rectangular specimen,loading static device based on a static axial stress wave propagation test,influence from the angle of energy on the static load stress wave propagation.The main contents and conclusions are as follows:(1)No matter in the loading or unloading condition,when the axial pressure is constant,the frequency spectrum curve points are the trend with the increase of the frequency increased firstly and then decreased finally to zero.Due to the fast attenuation of high frequency,slow attenuation of low frequency,under the influence of the difference of the high and low frequency attenuation speed,the main frequency of stress wave is attenuated with the increase of propagation distance.Internal fracture distribution of red sandstone is complex,the closure of the old crack and the formation of the new crack successively or simultaneously,resulting in two under the conditions of frequency with axial stress changes are different,the main frequency of the loading increases first and then tends to be stable as well as the unloading increases first and then tends to be stable finally decreases with the increase of axial compression.(2)Under the two different conditions of loading and unloading,the total energy of the stress wave signal has a good linear relationship with the attenuation of the propagation distance,and the linear fitting correlation of unloading is higher than that of the fitting correlation when the load is loaded.Due to the effect of increasing static load and repeated impact leads to increased risk of the internal structure of sandstone fracture or closed,the initial energy is released or absorbed,causing mutations and stress wave energy superposition,lead,discrete loading unloading is large.(3)The increase of the static load leads to the decrease of the incident wave and the increase of the wave impedance,and the effect of different stress paths in different stages of both the total energy intensity is different,so that the loading conditions,the total energy with the axial pressure increases overall decreases and then tends to be stable,unloading condition,axial pressure increases with the total energy is increased first and then decreased and finally tends to be stable.(4)Under the two different conditions of loading and unloading,with the increase of axial pressure,the variation trends of the total energy with the propagation distance and the attenuation rate of the fitting curve are fast decrease firstly and then tends to be stable.Under axial compression,the old crack rapid closure,fast slow attenuation of total energy,the slope decreases rapidly,the decay rate decreased rapidly;the axial pressure is large,old fracture closure and produce cracks,the total energy attenuation little overall change,namely the fitting slope and the decay rate tends to be stable.(5)Due to the development of the fracture,the fracture degree increases,the wave velocity is reduced,the high frequency component is absorbed by a large amount,the frequency spectrum is changed,the waveform is wide,and the result is dominated by low frequency components.But the sandstone has a number of primary cracks,resulting in the load and unload conditions,the frequency band 0~36.62 KHz energy accounts for the proportion of total energy is very high,the percentage of other band energy is very low.And the fast attenuation of high frequency,slow attenuation of low frequency,with the increase of frequency,the percentage of band energy is lower and lower.When the fracture is closed,the high frequency component attenuation decreases,the percentage increases,the percentage of low frequency components is reduced,the high frequency component attenuation increases,the percentage is decreased,and the percentage of low frequency component is increased.And the open closed crack under axial pressure control,so that in the two conditions although the percentage of large fluctuations,but the overall percentage of energy band 0~36.62 KHz with axial pressure decreases,and the rise of other bands overall energy percentage increase with the axial pressure.