Study On The Amplitude-frequency Characteristics Of Stress Waves In Red Sandstone With High Water Pressure And High In-situ Stress

Blasting excavation of deep high water pressure engineering rock mass,in the source of blasting in the distant area of the surrounding rock mass while under high water pressure,high in-situ stress and blasting dynamic load together,the rock engineering is subjected to dynamic load is the source of blasting load by the rock(mass)propagation attenuation results.If the stress wave propagation characteristics of high water pressure and high ground stress surrounding rock masses are known,predicting the attenuation results of blasting load propagation to the actual target of the established project is of great importance in assessing and controlling the stability of the surrounding rock masses in the adjacent middle and distant areas.In order to study the effects of different magnitudes of water pressure and in-situ stress on the propagation characteristics of rock stress waves,this paper uses a self-made high water pressure and high stress rock stress wave propagation test system to set up six water pressure and four axial static stress levels,and conducts a one-dimensional stress wave propagation test study on saturated red sandstone to investigate the propagation characteristics of rock stress waves under the action of high water pressure and high ground stress,respectively,in terms of stress wave amplitude and frequency domain variation characteristics.On the one hand,the stress wave amplitude is defined as the absolute value of the maximum peak value of each band,and the decay relationship of the stress wave amplitude with the change of water pressure and axial static stress is analyzed.On the other hand,the stress waveform is time-frequency transformed by fast Fourier transform,and the frequency domain characteristics of the stress wave are analyzed to characterize the effect of water pressure and axial static stress on the frequency domain characteristics of the stress wave with parameters such as the spectral peak,main frequency and centroid frequency.The main conclusions are as follows:(1)Fixed axial static stress variable water pressure,the reflected wave amplitude with the increase in water pressure are power function decrease,while the transmitted wave amplitude is power function increase,stress wave amplitude decay rate with the increase in water pressure is exponentially reduced.The incident and transmitted wave amplitudes decrease linearly with the increase of the axial static stress,while the reflected wave amplitude increases linearly,when fixed water pressure variable axial static stress.The interaction of water pressure and axial static stress affects the propagation properties of stress waves in rocks,The higher the axial static stress,the more sensitive the amplitudes of reflected and transmitted waves are to changes in water pressure.Compared with the high water pressure condition,the transmitted wave amplitude and reflected wave amplitude under no water pressure are more sensitive to the increase of axial static stress.(2)The stress wave spectra under each condition have similar shapes,and the main amplitudes are concentrated in the range of 0 ～ 8 k Hz,and the amplitudes show a trend of increasing and then decreasing to 0 with the increase of frequency.Fixed axial static stress variable water pressure,the higher the water pressure,the peak spectrum of the reflected wave is exponentially decreasing,the reflected wave amplitude increases with frequency and the slower the rate of decay,the peak spectrum of the transmitted wave is exponentially increasing,the transmitted wave amplitude increases with frequency and the faster the rate of decay.Fixed water pressure variable axial static stress,the higher the axial static stress,the higher the peak spectrum of the reflected wave,the faster the rate of decay of the reflected wave amplitude with increasing frequency,the lower the peak spectrum of the transmitted wave,the slower the rate of decay of the transmitted wave amplitude with increasing frequency.(3)The main frequency of the stress wave for each operating condition is within 1 ～ 2k Hz.Fixed axial static stress variable water pressure,the main frequency of the reflected wave rises with the increase of water pressure,while the main frequency of the transmitted wave first drops rapidly and then tends to be stable,the transmission wave frequency decreases within 0 ～ 4 MPa water pressure,and the higher the axial static stress,the faster the transmission wave frequency decreases.Constant water pressure variable axial static stress,With the increase of the axial static stress,the incident wave frequency rises and then decreases,and the reflected wave frequency decreases and then rises with the increase of the axial static stress,The main frequency of the transmitted wave under no water pressure increases with the increase of the axial static stress,but the main frequency of the transmitted wave under high water pressure tends to be smooth with the increase of the axial static stress.(4)Fixed axial static stress variable water pressure,the reflected wave centroid frequency increases with the increase of water pressure,the transmission wave centroid frequency decreases exponentially with the increase of water pressure,and the higher the axial static stress,the more sensitive the reflected and transmitted wave centroid-mass frequency changes with the increase in water pressure.Constant water pressure variable axial static stress,with the increase of axial static stress,the incident wave centroid frequency first increases and then decreases,the reflected wave centroid frequency first decreases and then tends to be constant under no water pressure,the reflected wave centroid frequency first decreases and then increases under high water pressure.The higher the water pressure,the more insensitive the transmission wave centroid frequency changes with the increase in axial static stress.