Mitigation of the seismic motion near the edge of cliff-type topographies using anchors and piles

Concentration of damage of buildings near the edge of cliff-type topographies has been observed during a number of recent earthquakes and interpreted by numerical dynamic analyses that illustrate the amplification of the horizontal acceleration and the generation of parasitic vertical acceleration near the tip of slopes. The paper performs a detailed parametric numerical analysis to investigate the ability of mitigating this topographic effect using anchors and piles. A typical field case, the Aegion slope of Greece, is considered. Different input motions are applied. The results illustrated that anchors and piles can be effective in mitigating the topographic effect. The main issue is that if the part of the slope in which topographic amplification occurs is connected to that at larger depths, in which the acceleration is smaller, then the accelerations at the top of the slope have to become more uniform and smaller. For typical diameter and material properties of anchors/piles the effectiveness of the mitigation depends on the length, inclination, location and number of anchors/piles. An optimum configuration of anchors/piles mitigating the topographic effect is proposed.     

Mitigation of the seismic motion near the edge of cliff-type topographies

Concentration of damage of buildings near the edge of hard or dense cliff-type topographies has been observed during a number of recent earthquakes. These observations have been interpreted by numerical dynamic analyses that illustrate the amplification of accelerations near the edge of slopes. The paper studies the effect of mitigating these accelerations using anchors both experimentally and numerically. The main issue is that if the part of the slope in which topographic amplification occurs is connected to that in which the acceleration is less, then the accelerations have to become more uniform. The experimental study involves dynamic centrifuge tests at the Cambridge University facility both with and without anchors. The numerical procedure was verified by the seismic response of the centrifuge tests. It was then applied to the study of the effect of anchors of a typical field case, the Aegion slope, under two different input motions. In all cases anchors were found effective in mitigating the seismic motion near the edge.     

Dynamical role of the Rocky Mountain controlled by East Asian topographies in modulating the tropospheric westerly jet in northern winter

本文通过数值模拟,研究了有无东亚地形存在时,落基山地形作用对冬季北半球副热带西风急流的影响,分析了东亚大地形对落基山地形的调制作用。结果表明,东亚地形的存在能够完全抑制落基山地形对太平洋副热带急流的加强作用,使得落基山地形作用仅能加强其下游的大西洋副热带急流。主要原因是东亚大地形可抑制落基山地形北侧反气旋环流的发展,进而抑制中纬度太平洋地区经向温度梯度的加强。该结果有助于我们进一步理解北半球大地形强迫作用,及其相互调制作用对对流层天气和环流结构的影响。