【摘要】 不同频率范围内的应力波在岩体的传播过程中,衰减系数对频率的依赖性具有显著差异。通过现场试验研究完整岩体对测井频率范围内应力波的滤波特性,针对常用黏弹性模型在描述衰减系数与频率关系存在不足,在频域上对黏性系数进行非定常处理,建立黏性系数非定常Maxwell模型,采用波形相关系数评价改进模型的滤波效果。研究结果表明,完整岩体总体上表现为低通滤波,在低通滤波范围内具有非等间距带通滤波特性,随传播距离增加,带通数逐渐减小;在吸收频率过渡带,应力波衰减系数随频率变化非常快,黏性系数非定常Maxwell模型能够有效描述应力波在完整岩体中的衰减系数变化规律;吸收频率过渡带的边界频率与传播距离成负指数关系,吸收频率过渡带的陡度参数可以近似认为是常数;随传播距离增加,黏性系数非定常Maxwell模型描述完整岩体的滤波效果明显提高,当传播距离为4.75m时,波形相关系数达到0.89,表明采用改进模型描述完整岩体是有效的。更多还原

【Abstract】 The effects of stress wave in different frequency ranges on attenuation coefficient are different. The filtering properties of stress wave propagating in intact rock mass within scope of log frequency were studied through field test. Based on the shortcoming of common viscoelastic model predicting the relationship between attenuation coefficient and frequency,Maxwell model for unsteady viscosity coefficient was established after the unsteady treatment of viscosity coefficient. The filtering effect of the improved model was evaluated using the waveform correlation coefficient. The study results indicated that intact rock mass has a low-pass filtering property and unequal interval band-pass property within scope of a low-pass filter, the number of band-pass decreases with increase in propagation distance; attenuation coefficients of stress wave with frequency change greatly in the transition zone of absorption frequency,the change rule of attenuation coefficient of stress wave propagation in intact rock mass is effectively described with the improved Maxwell model for unsteady viscosity coefficient; the boundary frequency of the transition zone of absorption frequency has a negative exponential relationship with propagation distance,the edge gradient parameter of the transition zone of absorption frequency is approximately constant. The filtering effect of intact rock mass improves obviously using the improved Maxwell model with increase in propagation distance; the waveform correlation coefficient reaches 0. 89 when propagation distance of stress wave is 4. 75m; the improved model is capable of describing the filtering properties of intact rock mass.更多还原