边坡地震响应及动力稳定性分析

发布时间：2018-03-20 06:43

本文选题：地震动力响应特征　切入点：加速度放大系数　出处：《西南交通大学》2013年硕士论文　论文类型：学位论文

【摘要】：我国是一个多山的国家,地震活动频繁,近几年各大地震所诱发的边坡失稳破坏如崩塌、泥石流、滑坡等地质灾害是山区常见的失稳破坏模式。目前对边坡失稳破坏的研究大多是从定性的角度来对滑动机理进行分析的,还需在数值模拟、理论计算等方面进行进一步研究,以评价边坡的地震动力响应稳定性。故积极开展边坡地震动力响应特征研究分析,对提高地震高发区及高烈度区的边坡治理质量与安全运行具有非常重要的理论意义和工程价值。本文以青海玉树机场路一不稳定边坡为例,并将其作为数值分析原型。通过FLAC3D有限差分软件,采用时程分析法,分别计算边坡在地震峰值加速度、持时、波谱特性,岩体粘聚力及弹性模量等参数不同取值下的加速度动力响应特征,进而得到其在坡体内分布规律的拟合公式。再进行拟静力法改进,即在现有拟静力法中考虑到加速度随边坡高度变化的非线性动力特征,从而计算出安全系数,评价边坡地震稳定性。最后分析同时考虑水平和竖向地震加速度作用条件下的边坡动力响应特征,为进一步分析地震稳定性奠定良好的基础。本文取得的主要研究成果有： (1)在水平地震波单独作用下,边坡对输入地震波存在显著的垂直放大效应和水平放大效应。地震峰值加速度放大系数随高程增加逐渐增大,一般在坡顶处达到最大值；同一高程处,由坡内至坡面,加速度放大系数呈增大趋势,在坡面处存在显著的临空面放大效应；并对加速度放大系数在边坡高程方向上的变化规律进行了公式拟合； (2)在加速度动力响应分析的基础上,对拟静力法进行了改进,改进的思想为在评价边坡地震稳定性时,考虑到边坡对地震加速度的非线性放大效应,采用拟合公式进行地震影响系数的计算,最后通过实例验证得出,改进拟静力法所计算的安全系数小于现有拟静力法,说明改进拟静力法更安全； (3)在水平和竖向地震波共同作用下,边坡对输入地震波存在显著的垂直放大效应和临空面放大效应。地震峰值加速度随高程增加逐渐增大,边坡底部放大效应不显著,增幅较小,边坡顶部会达到一个相对较显著的放大效应；同一高程处,由坡内至坡面,加速度放大系数呈增大趋势,在坡面处达到最大值。且通过加速度放大系数在坡体内的分布规律可知：在水平和竖向加速度共同作用下,边坡对地震加速度的水平放大效应较垂直向放大效应显著。
[Abstract]:China is a mountainous country with frequent seismic activities. In recent years, slope instability caused by major earthquakes, such as collapse and debris flow, Landslide and other geological hazards are common failure modes in mountain areas. At present, most of the researches on slope instability and failure are based on qualitative analysis of sliding mechanism, and need to be further studied in numerical simulation, theoretical calculation and so on. In order to evaluate the stability of the seismic dynamic response of the slope, the research and analysis of the characteristics of the seismic dynamic response of the slope are carried out actively. It is of great theoretical significance and engineering value to improve the slope treatment quality and safe operation in the areas with high earthquake incidence and high intensity. This paper takes the unstable slope of Yushu Chishang Road in Qinghai as an example and takes it as the prototype of numerical analysis. By using FLAC3D finite difference software and time history analysis method, the peak acceleration, duration and spectrum characteristics of the slope are calculated respectively. The acceleration dynamic response characteristics of rock mass under different parameters, such as cohesive force and elastic modulus, are obtained, and the fitting formula of the distribution law of rock mass in slope is obtained, and then the pseudostatic method is improved. That is to say, the nonlinear dynamic characteristics of acceleration varying with slope height are taken into account in the existing pseudostatic method, and the safety factor is calculated. Finally, the dynamic response characteristics of slope under horizontal and vertical seismic acceleration are taken into account, which lays a good foundation for further analysis of seismic stability. The main research results obtained in this paper are as follows:. 1) under the action of horizontal seismic wave alone, the slope has significant vertical amplification effect and horizontal amplification effect on the input seismic wave. The peak acceleration magnification coefficient increases gradually with the elevation increasing, and generally reaches the maximum at the top of the slope; At the same elevation, from the slope to the slope, the acceleration magnification coefficient tends to increase, and there is a significant magnification effect on the slope surface, and the law of the variation of the acceleration magnification factor in the direction of the slope elevation is fitted. 2) based on the analysis of the acceleration dynamic response, the pseudostatic method is improved. The improved idea is to take into account the nonlinear amplification effect of the slope seismic acceleration when evaluating the seismic stability of the slope. The fitting formula is used to calculate the seismic influence coefficient. Finally, the safety factor calculated by the improved pseudo-static method is less than that of the existing pseudo-static method, which shows that the improved pseudo-static method is safer. 3) under the joint action of horizontal and vertical seismic waves, the slope has significant vertical amplification effect and near-empty surface amplification effect on the input seismic wave. The peak acceleration of the earthquake increases gradually with the increase of height, but the amplification effect at the bottom of the slope is not significant. At the same elevation, the acceleration magnification coefficient increases from the slope to the slope. Through the distribution of acceleration magnification coefficient in the slope, it can be seen that the horizontal amplification effect of the slope on seismic acceleration is more significant than that of vertical acceleration under the combined action of horizontal and vertical acceleration.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU435

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