黄土场地地震动力响应及变形分析

Analysis of Seismic Response and Deformation in Loess Site

基于甘肃平凉大寨乡典型黄土塬地质构造为研究背景,以大型振动台试验方法获得的原始数据为依据,分析了加速度响应特征、频谱和反应谱变化,揭示了该黄土场地地震动反应特性,结合数值仿真模拟方法,对比了该黄土场地在单一地震荷载和累计地震荷载作用下加速度响应特征和位移变化特征。结果表明:黄土场地峰值加速度(PGA)和PGA放大系数与高程呈正相关性,PGA放大系数随地震动强度增大呈递减趋势;随着高程的增大,该黄土场地卓越频率缓慢向低频方向移动,卓越频率与输入地震动强度呈现负相关性;随着覆盖层厚度的增加,加速度反应谱峰值和特征周期先增加后减小,地震动强度增大时,特征周期向长周期方向偏移,幅值成倍增大;多烈度累计荷载作用对黄土场地的PGA放大系数影响较小,对水平位移的影响较为明显,抗震设计时应予以考虑。

Based on shaking table test data of loess plateau in Dazhai Township, acceleration response, the change of spectrum and response spectrum are analyzed, the seismic response characteristics of the loess site are then revealed. Moreover, the characteristics of acceleration response and displacement of the loess site under a single seismic load and cumulative seismic load are compared by numerical simulation. The results show that: the peak acceleration(PGA) and PGA amplification coefficient of the complex soil structure are positively correlated with the elevation and the amplification coefficient of PGA decrease with the increase in ground vibration intensity;the low frequency components become more abundant with increase in elevation of loess site, the excellent frequency was negatively correlated with ground vibration intensity;the peak value of acceleration response spectrum and characteristic period first increase and then decrease, with the increase of overburden thickness, and when the seismic intensity increases, the characteristic period is shifted to the long period, and the amplitude is multiplied;different loading modes have little influence on PGA amplification factor of the loess site, and the effect of horizontal displacement is more obvious.