| In order to obtain the lithological parameters of rock and soil,the wave method is applied in the Deqing Copper Mine and ShuangQi Mountain gold mining area,also the stress wave is studied in the joint rock,The variation of the rock mass is measured based on the waveform change,the results are compared with those through the drilling tool,The results are as follows:(1)Considering the influence of joint mass into stress waves propagation problem,the joint surface is treated as a Kelvin viscoelastic interface,the transmitted and reflected coefficient expression of harmonic waves across through the thick viscoelastic was calculated based on displacement potential function.The correlation coefficient was used to describe waveform changes,as wavelet across through the viscoelastic joint,then the application conditions of thick viscoelastic joint with some thickness which was analysed by displacement discontinuity model was discussed.the critical thickness was defined when the correlation coefficient of transmitted wave that calculated by thick viscoelastic joint model and displacement discontinuity model equaled to 0.9.The simplified displacement discontinuity model is used to describe the joint surface of the rock mass,and the effective method of determining the mechanical parameters of the joint surface is determined based on the principle of minimum variation of the waveform.There was little impact of the impedance ratio of rock mass and joint to the critical thickness;the relationship between the critical thickness and the center frequency followed as negative exponential law;and also the bigger incident angle,the lesser impact of center frequency to critical thickness.When the joint thickness is 0.03 m,the joint mechanics parameters are very close throurh both the displacement discontinuity model and the thick viscoelastic model;With the increase of the joint thickness and the center frequency of the wavelet,the deviation of the calculation result by the displacement discontinuity model is larger.The test results are consistent with the theoretical analysis.(2)The effect of rock mass viscosity on stress wave propagation is mainly manifested in velocity scatter and amplitude attenuation.The former is reflected by the change of the stress wave propagation velocity phase due to the frequency.The rock mass is regarded as the Kelvin viscoelastic medium,the measured waveform is disintegrated by the the Fourier series.According to the change of the phase when the stress wave passes through the viscoelastic rock,as a result studying the phase velocity dispersion characteristics.thereinto,the number of harmonics has a great influence on the decomposition of the waveform,when n equaled to 300 is sufficient tosatisfy the computational needs.assuming medium unsteady viscous coefficient presents: ?=a0f q,the parameters a0 equals to 1007600,q equals to 0.136 on the basement of P wave propagation laware calculated;the parameters a0 equals to 702861,q equals to 0.321 on the basement of SV wave propagation laware calculated.(3)The rock mass is regarded as the Kelvin semi-infinite medium.according to the stress wave viscous decay theory,the attenuation coefficient of the P-wave amplitude with the propagation distance is fitted to calculate the elastic modulus of the rock mass as E equals to 3.27 GPa.also the elastic modulus of the rock mass is calculated as the elastic modulus of the rock mass by 2.46 GPa.The elastic modulus of the rock mass is 1.33 times.assuming medium unsteady viscous coefficient presents: ? = a0 f q,the initial value of the viscous coefficient a0 equals to 7341,the steepness parameter q equals to 0.509 calculated on the basement of P wave propagation law;the initial value of the viscous coefficient a0 equals to 28594.6,the steepness parameter q equals to 0.231 calculated on the basement of SV wave propagation law. |
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