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针对现行水工抗震规范中对近断层地震缺乏考虑这一实际问题,首先讨论了近断层、远场地震动的差别,对比了近断层、远场地震动对地下洞室地震响应的影响,继而提出一种新的人工合成近断层地震动时程的方法,并采用合成的近断层地震动时程对某水电站地下洞室群进行了近断层地震稳定性专门研究。结果表明:与常规地震分析中考虑的远场地震动相比,近断层脉冲型地震动的主要特征为V max/Amax和D max/Amax(V max、D max、A max分别为速度峰值、位移峰值、加速度峰值)指标更大,且近断层脉冲型地震动的主要能量集中在1 Hz以下的频段;在相同峰值加速度幅值、相同反应谱的前提下,近断层地震动对高边墙、大跨度地下工程的破坏程度远比远场地震动大;较之前人的研究方法,文中提出的近断层脉冲型地震动合成方法考虑了[1/T p,1]Hz这一频段内的地震波信息,更具合理性;在设定的计算条件下,地下厂房洞室群有在近断层地震动作用下发生失稳的危险性,需要进一步针对近断层地震动进行专项风险性评价,以讨论是否需要增设针对性的抗震支护措施。
Aiming at the lack of consideration of near-fault earthquakes in the current hydraulic code, this paper first discusses the difference of near-fault and far-field earthquakes and compares the effects of near-fault and far-field earthquakes on the seismic responses of underground earthquakes. A new method of artificial synthetic near-fault ground motion time-history is proposed, and the near-fault seismic stability of underground caverns in a hydropower station is studied by using synthetic near-fault ground motion time history. The results show that the main characteristics of near-fault impulsive ground motions are V max / Amax and D max / Amax (V max, D max, A max, respectively) compared with the far-field ground motions considered in conventional seismic analysis. Peak and acceleration peaks), and the main energy of near-fault impulsive ground motion concentrated in the frequency band below 1 Hz. Under the same peak acceleration amplitude and the same response spectrum, The damage degree of long-span underground engineering is far greater than that of far-field earthquakes. Compared with previous research methods, the synthetic method of near-fault impulsive ground motions proposed in this paper considers the seismic wave information in [1 / T p, 1] Hz , More reasonable; under the set calculation conditions, the cavern group of underground powerhouse has the risk of instability under the action of near-fault ground motions, and further special risk assessment on near-fault ground motions is needed to discuss whether it is necessary Add targeted anti-seismic support measures.