断层场地对地震波的放大作用

发布时间：2018-11-03 15:21

【摘要】：非发震断层广泛存在于地壳中,作为场地条件影响地震波的传播。因此研究断层破碎带对地震波的放大作用,具有重要的理论意义和工程实践价值。本文利用有限元分析程序FLUSH,结合一致传递边界,计算了含破碎带均匀场地和层状场地的线性和非线性地震反应。全面分析了破碎带宽度、刚度、倾角和输入地震波频谱特性对地震动放大作用的影响;比较了破碎带对地震波非线性放大作用与线性放大作用的差别;详细分析了在线性和非线性情况下,含破碎带层状场地与等效均匀场地对地震动放大作用的不同。研究表明:断层破碎带对附近地表水平加速度具有显著的放大作用,放大作用峰值出现在破碎带附近及断层上盘。破碎带上盘各点反应谱卓越周期明显比较长,而破碎带下盘各点反应谱卓越周期则比较短。破碎带宽度越大,破碎带附近地表加速度峰值越大;破碎带刚度越低,地表加速度反应峰值越大;随着破碎带倾角的增大,加速度反应最大峰值位置逐渐向破碎带上盘方向偏移。考虑了土体的非线性特性后,非线性情况竖向加速度最大峰值在某些情况下可以达到水平加速度最大峰值,非线性情况水平加速度最大峰值完全可能大于线性情况,且非线性情况竖向加速度最大峰值可以显著大于线性情况。因此,对工程振动问题,应根据工程的重要性适当进行非线性动力分析。层状场地中破碎带对地震波的放大作用显著大于等效均匀场地。考虑了土体的非线性特性后,层状场地相对于均匀场地的放大倍数明显大于线性情况。也就是说,在含破碎带层状场地的非线性动力分析问题中,按《规范》方法采用等效的均匀场地模型代替层状场地模型,会产生比线性情况更大的误差。输入地震波的频谱对地震动的放大作用有着重要的影响,该影响与场地土体的动力特性密切相关。对于场地非线性动力分析问题,在考虑了破碎带对地震波的散射后,地震波与场地土体的共振现象可能会因散射本身的复杂性也变得非常复杂。
[Abstract]:Non-seismogenic faults are widely found in the earth's crust, which, as site conditions, affect the propagation of seismic waves. Therefore, it is of great theoretical significance and practical value to study the amplification of seismic waves by fault fracture zone. In this paper, the linear and nonlinear seismic responses of uniform site and layered site with fractured zone are calculated by using the finite element analysis program FLUSH, and uniform transfer boundary. The influence of the width, stiffness, inclination angle and spectrum characteristics of the input seismic wave on the ground motion amplification is analyzed, and the difference between the nonlinear amplification and the linear amplification of the seismic wave by the broken zone is compared. In the case of linear and nonlinear, the difference of the amplification of ground motion between the layered site with broken zone and the equivalent uniform site is analyzed in detail. The results show that the fault fracture zone has a significant amplification effect on the horizontal acceleration of the surface near the fault zone, and the peak value of the amplification effect occurs near the fracture zone and the upper disk of the fault. The excellent period of each point response spectrum in the breakage band is obviously longer than that in each point response spectrum in the breakage band, but the outstanding period of each point response spectrum in the broken band is relatively short. The larger the width of the broken zone, the greater the peak value of the ground acceleration near the broken zone, the lower the stiffness of the broken zone, the greater the peak value of the surface acceleration response. With the increase of the angle of the breakage zone, the maximum peak position of the acceleration response gradually shifts to the disk direction of the broken zone. After considering the nonlinear characteristics of soil, the maximum vertical acceleration peak can reach the maximum horizontal acceleration peak in some cases, and the maximum horizontal acceleration peak value in the nonlinear case is probably larger than that in the linear case. The maximum vertical acceleration peak in nonlinear case can be significantly larger than that in linear case. Therefore, nonlinear dynamic analysis should be carried out according to the importance of engineering. The amplification effect of broken zone on seismic wave in layered site is significantly larger than that in equivalent homogeneous site. Considering the nonlinear characteristics of soil, the amplification ratio of layered site to uniform site is obviously larger than that of linear situation. That is to say, in the nonlinear dynamic analysis of layered sites with fractured zones, the equivalent uniform site model is used to replace the layered site model according to the "gauge" method, and the error is greater than that in the linear case. The frequency spectrum of the input seismic wave has an important effect on the amplification of the ground motion, which is closely related to the dynamic characteristics of the site and soil. For the nonlinear dynamic analysis of the site, the resonance phenomenon between the seismic wave and the ground soil may become very complicated because of the complexity of the scattering itself after considering the scattering of seismic waves by the broken zone.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU435

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