Finite Element Analysis Of The Influence Of The Slope Topography On Seismic Acceleration Spectrum

The effect of the topography to the earthquake has been one of the problems in which the scientists are interested.The amplification effect was found near the irregular region,in both observed data on site and numerical modelling.To study the level and range of the amplification effect of the step-shape topography,the acceleration value and characteristic was analyzed by numerical modelling.In this paper,the numerical models were built to study this problem.The dynamic response of the slope under earthquake belongs to the scattering problems of wave in semi-infinite half space.Every kind of artificial boundaries which were used to absorb the energy of the reflected wave were introduced,and the theory of these boundaries were also discussed.According to their characters the appropriate boundaries was chosen.The reliability of the boundary was proved by the fundamental models.The acceleration of the monitor points were obtained by the numerical models,then transferred to response spectrum of the acceleration and compared with that of the free field.The study showed that when modeling the scattering problems,if the wave were transferred to equivalent acceleration,the viscoelastic boundary would be invalid.To keep the reliability of the boundary,the wave should be transferred to equivalent load.The amplification factor of the earthquake was related to the height,angle and shape of the slope;the higher of the slope,the larger of the amplification and the larger of the angle of the slope,the larger of the factor.For the rocky slope whose height is smaller than 60 m,the amplification factor of the horizontal earthquake was smaller than 1.6,and the amplification factor of the monitor point that 8H away from the slope crest was smaller than 1.1,and amplification factor of the monitor point that 10 H away from the slope crest was smaller than 1.03.The amplification effect of the vertical earthquake wave was concentrated in the region in 2H from the slope crest,so this region was highly important.The shape of the slope would affect the amplification effect.For both the convex and concave shaped slope,the amplification effect would be heightened.