地震作用下反倾岩质斜坡动力响应规律及频谱特征研究

以四川昌都贡扎滑坡为原型,设计制作了1∶1 000的振动台试验模型,开展了包含软弱岩性组合和贯通性结构面的反倾岩质斜坡的振动台模型试验。考虑场地工程地质条件和场地特性,将富含多种频率的人工合成基岩地震波作为动力输入条件,探讨了不同概率水准人工合成地震波作用下反倾岩质斜坡的动力响应规律,并与输入正弦波的放大效应规律进行对比;通过对不同类型地震波输入下竖向监测点所得数据进行频谱分析,研究其对反倾岩质斜坡的动力响应影响机制。试验结果表明,在人工合成地震波作用下,加速度放大系数沿坡面和竖直方向均具有明显的高程放大效应,沿水平方向具有明显的趋表效应;人工合成地震波作用下得到的坡表和坡内响应规律与正弦波作用下类似,但是趋表效应不尽相同。正弦波作用下,斜坡监测点的频谱图为一条竖向直线,衍生的特征频率为输入正弦波频率的整数倍;人工波和天然波有更复杂的频段分布,斜坡对地震波高频段的放大作用明显高于低频段;但无论正弦波还是人工合成波,卓越频率越接近斜坡自振频率,斜坡动力响应越明显。对比不同类型地震波频谱图发现,由于正弦波波形简单,经斜坡传播后各测点频谱图变化不明显,不能准确反应岩质斜坡对输入地震波的影响,...

Dynamic response and spectrum characteristics ofanti-dip rock slopes under earthquake

Taking the Gongza landslide in Changdu City,Sichuan Province as the prototype,a 1:1000 shaking table test model was designed,and the shaking table model tests of anti-dip rock slopes with weak lithologic association and a penetrating structural plane were carried out.Considering the engineering geological conditions and site characteristics,the dynamic response law of the anti-dip rock slope under artificial seismic waves with various frequencies was discussed,and then compared with the amplification effect law under the input of sine wave.Based on the spectrum analysis of the data obtained from vertical monitoring points under different types of seismic waves,the dynamic response of anti-dip rock slope was studied.The results show that under the action of artificial seismic wave,the acceleration amplification coefficient shows obvious elevation amplification effect both along the slope surface and the vertical direction,and shows obvious skin effect along the horizontal direction.Under the action of artificial seismic wave,the slope and in-slope responses are similar to those under the action of sine wave,but the skin effect is not the same.Under the action of sine wave,the spectra of slope monitoring points show a vertical straight line,and the derived characteristic frequency is an integral multiple of the input sine wave frequency.The artificial and natural waves have more complex frequency distribution,so the amplification effect of the slope on the high frequency band is obviously higher than that on the low frequency band.However,the closer the predominant frequency of sine wave and artificial wave is to the natural frequency of the slope,the more obvious the slope dynamic response is.By comparing the frequency spectra of different types of seismic waves,it is found that due to the simple waveform of sine wave,the frequency spectrum of each measuring point does not change obviously after propagating through the slope,so it can not accurately reflect the influence of rock slope on the input seismic wave.Therefore,the sine wave is not recommended to be used as the dynamic input wave when studying the spectral characteristics of rock slopes.