含软弱夹层岩质边坡的模态分析及其对边坡地震动力响应影响的初步研究

本文以含软弱夹层岩质边坡作为研究对象,基于数值软件ANSYS的模态分析给出了含不同倾角与厚度软弱夹层边坡的前5阶固有频率与振型,并分析了夹层倾角和厚度对边坡固有模态的影响。接着,结合已有的大型振动台模型试验结果,在小应变范围内讨论了边坡的固有模态与其动力响应特性之间的关系。结果表明:(1)在夹层倾角相同时,含较厚软弱夹层边坡固有频率低于含较薄软弱夹层边坡;(2)在夹层厚度相同时,随着倾角增加,夹层从反倾变化到顺倾,低阶(1、2)固有频率也逐渐增加,而高阶(3、4、5)固有频率则呈下降趋势;(3)从第3、4阶开始,边坡变形受夹层影响增强;(4)基于加速度傅里叶谱比分析得出的边坡响应放大频率与边坡前5阶固有频率范围接近,加速度和位移响应在夹层及以上部位响应强烈,与边坡前5阶振型较为一致,预示了边坡的共振响应。需要指出的是,本文得出的结论尚且不能用于准确解释边坡在大变形及破坏阶段的动力响应特征,但可为边坡动力特性及共振响应的深入研究提供思路。

Modal analysis of rock slope with a weak interlayer and its influence on seismic dynamic response of slope

Based on modal analysis of the rock slope with a weak interlayer with software ANSYS,the first five order natural frequencies and modes of the slope were calculated,and the influence of the dip angle and thickness of the weak interlayer on the natural modes of the slope was analyzed.Then the relationship between the natural modes of the slope and its dynamic response was discussed based on the completed large-scale shaking table model test.The results show that:(1)with the same dip angle of the interlayer,the natural frequency of a slope with a thicker weak interlayer is lower than that of a slope with a thinner weak interlayer;(2)with the same interlayer thickness,the natural frequencies of low-order(1 st,2 nd)modes increase as the dip angle is increased and the interlayer changes from anti-dipping to consequent,while the natural frequencies of high-order(3 rd,4 th,5 th)modes decrease gradually;(3)since from the 3 rd and 4 th order vibration modes,the influence of weak interlayer on the slope deformation is enhanced;(4)based on the Fourier spectrum ratio analysis of accelerations,the frequencies where the response is amplified are close to the first five natural frequencies.The strong acceleration and displacement responses occur around the interlayer and above,which is consistent with the first five vibration modes of the slope.The consistence indicates the resonance response of the slope.It should be pointed out that the conclusion drawn in this paper cannot be used to accurately explain the dynamic response characteristics of the slope in the stage of large deformation and failure,but it can provide ideas for the in-depth study of the dynamic characteristics and resonance response of the slope.