夹杂与地形对地面地震动的影响

发布时间：2018-04-24 10:36

本文选题：无量纲 + 二维有限元方法　；参考：《中国地震局工程力学研究所》2015年硕士论文

【摘要】：盆地、局部不规则地形和地下夹杂等复杂场地对地震动有显著影响,建筑的选址和抗震设防越来越重视复杂场地的放大效应。本文研究了二维SH波入射下,地下圆形夹杂以及典型的凹陷和凸起地形对地震动的影响,结合芦山地震强震记录分析了局部不规则地形的影响。具体研究工作包括:1.引入了模型的无量纲参数,并通过数值计算验证了模型无量纲化的可行性。2.利用二维有限元方法和谱比法从时域和频域分析研究空穴、软弱和坚硬夹杂对地震动的影响规律。研究表明:软弱夹杂和空穴对地表地震动有较大放大作用,且放大的规律较为相近,在地表的放大位置也相同,其中软弱夹杂对入射波频率更敏感,对地表放大倍数更大;坚硬夹杂主要表现为屏障作用,对地表放大作用较小,其影响几乎可以忽略。3.利用二维有限元方法和谱比法从时域和频域研究凹陷和凸起地形在垂直和斜入射下对地面运动的影响规律,并分析了凹陷和凸起地形随深宽比和高宽比的变化对地面运动影响的变化规律。研究表明:凹陷地形对地形上的点放大相对较小,对附近地平面的点放大较大,斜入射时在迎波面一侧角点位置放大最大,随着凹陷地形深宽比的增大,地形的放大作用增大;凸起地形则对地形上的点放大较大,对附近地平面的点放大较小,斜入射情况下,凸起地形上入射波能直达的区域受到的最大放大作用最大,迎波面地平面的最大放大作用次之,背波面地平面和地形上的影区以及角点的放大作用相对较小,垂直入射情况下,凸起地形的顶点放大最大,随着凸起地形高宽比的增大,凸起地形顶点受到的放大作用增大,其余点的放大作用先增大后减小。4.结合芦山地震主震以及41次余震在4个地形不同的相邻台站的强震记录,采用传统谱比法(RSM)和水平分量与垂直分量谱比法(HVSR)分析地形的影响。研究表明:4个台站受地形的影响都有较大的放大作用;余震记录分析表明处于山腰的51BXZ台放大作用大于处于山脚的51BXD台,51BXZ台在3Hz左右有很明显的放大,在8-14Hz也有一定的放大,51BXD台则在5-10Hz范围都有相对较小的放大;主震在51BXZ台记录的幅值小于51BXD台的原因可能是受限于震级较大时土层非线性的影响。
[Abstract]:Complex sites, such as basins, local irregular topography and underground inclusions, have a significant impact on ground motion. The site selection and seismic fortification of buildings pay more and more attention to the amplification effect of complex sites. In this paper, the effects of underground circular inclusions and typical depression and uplift topography on ground motion under the incidence of 2-D SH wave are studied. The influence of local irregular topography is analyzed based on the strong earthquake records of the Lushan earthquake. Specific research work includes: 1. The dimensionless parameters of the model are introduced, and the feasibility of dimensionless model is verified by numerical calculation. Two dimensional finite element method and spectral ratio method are used to study the influence of holes, weak and hard inclusions on ground motion in time and frequency domain. The results show that the weak inclusions and holes have larger magnification effect on the ground motion, and the law of magnification is similar, and the magnifying position of the weak inclusions is also the same. The weak inclusions are more sensitive to the frequency of incident waves and more magnified to the surface. The hard inclusion is mainly a barrier effect, but it has little effect on the surface magnification, and its influence can be almost ignored. 3. Using the two-dimensional finite element method and spectral ratio method, the effects of depression and uplift topography on ground motion under vertical and oblique incidence are studied in time and frequency domain. The influence of the depth to width ratio and the aspect ratio on the ground motion is analyzed. The results show that the point magnification is relatively small in the sag terrain and larger in the nearby ground plane, and the angle position at the side of the wave face is the largest when oblique incidence occurs. With the increase of the ratio of depth to width of the depression terrain, the magnification effect of the topography increases. On the other hand, the point magnified by the raised terrain is larger than that by the ground plane nearby. The maximum magnification of the area with direct incident wave energy on the convex terrain is the largest in the case of oblique incidence. The maximum magnification of the ground plane is the second, and the magnification of the shadow area and the corner point on the back wave plane and terrain is relatively small. In the case of vertical incidence, the maximum magnification of the vertex of the raised terrain is obtained, and with the increase of the aspect ratio of the raised terrain, The magnification of the topographic vertices is increased, and the magnification of the other points increases first and then decreases. 4. Combined with the strong seismic records of the Lushan earthquake main shock and 41 aftershocks in four adjacent stations with different topography, the influence of topography was analyzed by using the traditional spectral ratio method (RSM) and the horizontal and vertical component spectral ratio method (HVSRs). The results show that the four stations are greatly magnified by the topography, and the aftershock records show that the magnification effect of the 51BXZ station at the mountainside is larger than that of the 51BXD station 51BXZ at the foot of the mountain. The amplitude of the main shock recorded in the 51BXZ station is smaller than that of the 51BXD station, which may be due to the nonlinear effect of the soil layer when the magnitude of the main shock is larger than that of the 51BXD station.
【学位授予单位】：中国地震局工程力学研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.9

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