摘要
20世纪中期以来,我国所发生的多次强震中,大量的土石坝遭受地震破害,这些震害资料说明,不仅土石坝本身的材料特性、边界条件、几何尺寸对其地震响应有影响,而且地震波的入射方向对其影响也很大。虽然由地壳深部往地表传播的地震波,经过多次折射和反射后,入射方向将是接近于垂直于水平地表的竖直方向；但是世界上绝大多数地震是浅震源,地震波入射方向是不定的；地震波沿不同的方向输入,结构中将产生不同的地震响应,只有在某一特定的地震波输入方向下,结构物内某点或某截面的某一应力或内力值才达到最大值,此时地震波的入射方向即为最不利的入射方向。本文针对高土石坝最不利输入方向问题的研究完成了如下几方面研究工作。
(1)研究了地震动的输入形式,根据土石坝坝型特点,本文选用分解地震惯性力的方法解决地震动倾斜输入问题。
(2)对土石坝抗震稳定分析方法进行了比较研究。采用有限元法和非线性等价粘一弹性模型对土石坝进行三维动力分析,对地震动的形式、地震动的入射角度和坝高等因素的影响进行了研究的,通过工况计算分析最后得出土石坝地震动的最不利输入角度,及地震响应的最剧烈位置。
(3)以紫坪铺面板堆石坝为例,分析了最不利地震动输入角度。
Since the 1960s, more than ten strong earthquakes have happened, and a large amount of earth-rock dams have been destructed. The data of the earthquakes suggest that seismic response is not only related to the the material properties, boundary conditions and geometrical dimension, but also is related to the incident direction of earthquake waves. The incident direction of surficial seismic waves propagated from the deep crust is close to the incident direction perpendicular to the horizontal surface, However, most of earthquakes are shallow seismic source in the world, their incident direction is unsteady. When seismic waves are input from different direction, There will be different seismic response in the structure. Only when the seismic waves are input in a particular direction, can the stress or internal force in the structure achieve maximum. In this case, the seismic incident direction is considered as the most unfavorable incident direction. The paper studies the most unfavorable incident direction for earth-rock. The main contents are as following:
Firstly, the paper studies the form of the input of seismic waves. The paper chooses the method of decomposition of inertial force to solve tilt input problem of earthquake waves.
Then, the paper analyzes the seismic stability methods comparatively. The paper also studies different input forms of seismic waves, incident direction of seismic waves, and the influence of the height of the dam with the finite element method and nonlinear equivalent stick-elastic models. Through calculation and analysis, the paper gets the most unfavorable direction and the strongest response of position for earth-rock dam under seism load.
Finally, the paper takes the zipingpu concrete-faced rockfill dam as an example and verifies the accuracy and applicability of the conclusions.
引文
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