A three-dimensional entity model for the 19th grotto's west side cave of Yungang Grottoes was built in order to explore the seismic dynamic responses of grottoes, A finite difference software, FLAC3D, was used to numerically simulate the displacement, acceleration amplification factor, stress distribution and acceleration Fourier spectrum of its chamber and surrounding rock. The simulation results show that its external cliff has a trend of outward collapse, and the main failure mode of rock mass is shear failure. Seismic waves are reflected and superimposed on each other in the region near the chamber, and large energy is absorbed by rock mass, so earthquake acceleration in the region should be augmented in antiseismic strengthening design.%为探索石窟地震动力响应,建立了云冈石窟第19窟西侧耳窟的三维实体模型,并用有限差分软件FLAC3D对耳窟进行了地震动力模拟计算,分析了硐室岩体位移、加速度放大系数、应力分布和加速度傅里叶谱.数值模拟结果表明:地震作用下,该窟外立面岩体有外倾和塌落的趋势；石窟岩体的破坏模式以剪切破坏为主；地震波在耳窟所在高程范围的岩体内经多次反射、叠加,能量损耗较大,耗散的能量被该区域的岩体吸收,因此,进行抗震加固设计时,应适当提高此区域的地震加速度.
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