关键词: 黄土塬, 强震动观测, 振动台试验, 数值模拟, 动力响应, 放大效应

Abstract: The 2008 Ms8.0 Wenchuan earthquake had caused serious damage to structures in loess tableland region far away from the epicentre, the earthquake damage and the amplification effects of ground motion on local sites were significant. Using the typical loess tableland as the object of investigation, the dynamic response characteristics of loess tableland slope under the action of strong vibration were systematically studied by applying mobile ground motion observation arrays and numerical analysis. Based on large-scale shaking table test and numerical simulation, the change rules of surface acceleration responses of loess tableland with different thicknesses under different actions of Wenchuan earthquake were analyzed, and the potential effects on the earthquake damage were studied. The results show that: 1) The phenomenon of low predominant frequency corresponding to high peak ground acceleration (PGA) amplification at the top of loess tableland slope may be related to the ratio of slope height difference to incident wave length. 2) The loess tableland with a slope gradient ranging from 60o-70o has the most significant amplification effects on ground motion. The PGA on top of slope can be amplified by 2 times, the predominant period can be increased by 5 times. 3) The amplification effects on ground motion are predominant for thick loess tableland, PGA horizontal amplification coefficient potentially subject to an increase by 2 times and seismic intensity by 1 degree. 4) Along with the increase of loess thickness, the predominant period of response spectrum increases, so that buildings with natural period ranging from 0.7 to 2.0 seconds or greater than 3 seconds will undergo obvious horizontal amplification effects.

Key words: loess tableland, ground motion observation, shaking table test, numerical simulation, dynamic response, amplification effect