摘要
2008年汶川M_(S)8.0地震现场的震害调查资料显示,河流阶地地形对建筑物震害分布的影响规律表现为:阶地前缘冲洪积层较厚区域的建筑物遭受了严重的破坏,而阶地后缘坡积层较薄区域受损则相对较轻,总体上呈现出前缘震害显著大于后缘的特征。为研究该震害特征的机制,利用有限差分软件FLAC3D构建三维阶地模型,模拟分析了脉冲荷载作用下阶地模型的地震动响应。结果表明:各级阶地前缘的地震动水平均显著高于后缘,同时随着上覆土层的增厚,峰值加速度、相对持时值、反应谱平台值以及放大系数均呈现上升趋势;随着阶地级数的减小,峰值加速度、持时和反应谱特征周期均呈下降趋势,且随着模型阶地级数的增加,对地震动低频成分的放大效应也显著增强。因此,阶地级数和上覆土层厚度是影响地震动响应的关键因素,高阶地和厚覆盖土层区域对地震动的放大效应更强,建筑物遭受的破坏更严重。
The seismic ground motion topographic effect,as an important research content in the field of seismic engineering,the study on the mechanism of the effect of complex terrain on the ground motion characteristics can provide basis for engineering seismic defense.A large number of post-earthquake site investigations have shown that the complexity of local terrain has a significant impact on the distribution of seismic damage,especially the irregular terrain can change the intensity and spectral characteristics of ground motion.As a type of locally irregular topography widely existing in nature,the unique geometric shape of river terraces can cause complex scattering and diffraction of seismic waves,resulting in variation of ground mo-tion in its local areas,and then affecting the seismic damage degree of surrounding buildings.Based on on-site seismic damage investigation data of the river terraces during Wenchuan M_(S)8.0 earthquake in 2008,buildings in the area with thicker alluvial deposits at the front edge of the terrace suffered severe damage,while those in the area with thinner slope deposits at the rear edge of the terrace suffered relatively mild damage.In general,the seismic damage at the front edge was significantly greater than that at the rear edge.At the same time,in order to study the mechanism of this seismic damage feature,the river terraces were selected as the re-search object,and the finite difference software FLAC3D is used to establish three-dimensional river terrace analysis models with different thicknesses of overburden soil layers,and then sim-ulate and calculate the ground motion response under impulse loading,thus further revealing the influence law and internal mechanism of river terrace topography on ground motion characterist-ics and the distribution of seismic damage to buildings.For the same order terrace,the peak values of the horizontal and vertical acceleration and the 90%energy duration all show an upward trend with the increase of the overlying soil thick-ness,reaching the maximum value at the front edge of the terrace and the transition point with the steep slope.Meanwhile,the ground motion level at the front edge of each terrace is signific-antly higher than that at the rear edge.As the terrace order decreases,the peak values of the ho-rizontal and vertical acceleration and the 90%energy duration at the corresponding area also gradually decrease.Similarly,the trend of the Fourier spectrum amplitude and ratio at different monitoring points on the same order terrace is basically consistent,but the amplitude and ratio increase gradually as the monitoring point approaches the edge of the terrace facing the steep slope and the front edge of the area with increased soil thickness.As the terrace order increases(the terrain height rises),the natural frequency of the structure increases accordingly,thereby significantly enhancing the amplification effect of low-frequency ground motion.The character-istic period Tg,platform value,and platform amplification coefficientβin the standard re-sponse spectrum of seismic acceleration for different monitoring points are all affected by the terrace order and overlying soil thickness.The Tg value decreases gradually as the terrace order decreases;the platform value increases as the overlying soil thickness at the front edge of the terrace increases;however,the platform amplification coefficientβdecreases as the terrace order increases,and the amplification coefficient at the front edge of the terrace is significantly larger than that at the rear edge.River terraces have a significant impact on the propagation of ground motion and the seis-mic damage degree to buildings.The change in the thickness of the overlying soil layer leads to different distributions of building damage by affecting the amplification of ground motion,while the terrace orders exacerbate or mitigate the seismic damage by affecting the spectral char-acteristics and overall level of ground motion.Therefore,the terrace orders and overlying soil thickness are the key factors affecting ground motion response,and the amplification effect of ground motion is stronger in high terrace and thick covering soil layer,which leads to severe damage of buildings.
作者
熊文
王伟
杨研科
徐凯放
赵宁康
曹子昂
李昀松
Xiong Wen;Wang Wei;Yang Yanke;Xu Kaifang;Zhao Ningkang;Cao Zi'ang;Li Yunsong(Institute of Disaster Prevention,Hebei Sanhe 065201,China)
出处
《地震学报》
2025年第5期695-710,共16页
Acta Seismologica Sinica
基金
中国地震局地震科技星火计划项目(XH23062A)资助.
关键词
汶川
M_(S)8.0
地震
河流阶地
建筑物震害
数值模拟
Wenchuan M_(S)8.0 earthquake
fluvial terrace
seismic damage to buildings
nume-rical simulation
作者简介
熊文,在读硕士研究生,主要从事地震动地形效应研究,e-mail:1090531391@qq.com;通信作者:王伟,博士,副教授,主要从事强震动观测和强地面运动研究,e-mail:wwwiem@163.com。
