含软弱夹层顺层岩质边坡传递函数及其应用研究

Research on transfer function of bedding rock slope with soft interlayers and its application

基于大型振动台模型试验及传递函数理论,对含软弱夹层顺层岩质边坡的绝对传递函数和相对传递函数进行了对比分析,探讨了两种传递函数计算边坡动力特性参数的准确性,并对利用传递函数估算边坡频域动力响应的可行性进行了研究。研究结果表明,采用坡面及坡内加速度时程计算得到的传递函数曲线形态相近,幅值差别较小;相对传递函数实部比绝对传递函数实部小1,绝对传递函数和相对传递函数虚部重合,且两种传递函数虚部峰值两侧对称性较好,利用传递函数虚部计算边坡动力特性参数准确性较高。在频率大于10 Hz部分,相对传递函数模趋于1,绝对传递函数模趋于0。利用两种传递函数虚部及相对传递函数模计算得到的边坡固有频率十分接近。两种传递函数模计算得到的阻尼比比较准确,计算结果表明,含软弱夹层顺层岩质边坡的阻尼比大于均质岩质边坡。利用两种传递函数虚部及模计算得到的含软弱夹层顺层岩质边坡加速度振型相同。利用绝对传递函数估算含软弱夹层顺层岩质边坡频域动力响应的准确性高于相对传递函数估算结果。利用传递函数对输入地震动的频谱特性进行修正有利于保证含软弱夹层顺层岩质边坡动力响应研究输入机制的合理性。

A large scale shaking table test was conducted on the bedding rock slope with soft interlayers in this paper. Based on the transfer function theory, we analyzes the relative transfer function and absolute transfer function of this slope. The effect of these two kinds of transfer function on function characteristics and the calculation of seismic parameters is studied. The feasibility and accuracy of estimating the frequency domain response by the transfer function is also analyzed. The results show that the transfer functions calculated by the acceleration near slope face and in the middle of slope body have similar form, and there is small amplitude difference. The real part of relative transfer function is less 1 than that of absolute transfer function. The imaginary part of two kinds of transfer function is the same, and both sides of imaginary part have a high degree of symmetry. Thus seismic parameters calculated by the imaginary part have high accuracy. When the frequency is greater than 10 Hz, the module of relative transfer function is close to 1, while the module of absolute transfer function is approximately 0. The natural frequency obtained by the imaginary part is similar to that calculated by the module of relative transfer function. The damping ratios calculated by the modules of relative and absolute transfer functions are accurate. This study shows that the damping ratio of bedding rock slope with soft interlayers is lager than that of homogenous rock slope. The acceleration mode calculated by the imaginary part is the same as that by module of two kinds of transfer function. The estimation of frequency domain seismic response of bedding rock slope with soft interlayers by absolute transfer function is more accurate than relative transfer function. The correction of spectral characteristics for input ground motion can guarantee the reasonable mechanism of input ground motion on dynamic response of bedding rock slope with soft interlayers.