映秀地区岩浆岩边坡地震动力响应规律研究

发布时间：2018-01-25 00:46

  本文关键词： 映秀 岩浆岩 边坡 发育规律 地震 动力响应 数值模拟　出处：《成都理工大学》2013年硕士论文　论文类型：学位论文

【摘要】：在我国西部峡谷区，边坡地震动力响应问题突出。汶川地震诱发了大量边坡次生灾害，加剧了震区的破坏和损失，震后余震频发，使得部分边坡再次破坏失稳。因此，对震区边坡地震动力响应规律的研究具有重要的理论意义和现实意义。 本文以汶川地震震中区映秀-北川断裂上盘元古代岩浆岩边坡为研究对象，在详实的现场调查资料基础上，利用统计分析和数值模拟分析的方法，对区内边坡地质灾害的发育规律及影响因素进行分析，进一步研究了地震荷载和边坡地形地貌条件对边坡地震动力响应规律的影响，并以老虎嘴崩塌为例，模拟分析其动力响应规律。研究成果如下： （1）研究区属中--高山峡谷地貌，地层岩性以岩浆岩为主，地质构造复杂，地震活动频繁，河谷走向与优势节理方向呈大角度相交。 （2）区内中-大型崩塌占震后边坡地质灾害的90%，主要沿岷江干流及其支流两岸呈线状分布，干流右岸崩塌无论是密集程度还是规模上都大于左岸（背坡效应），边坡破坏模式以滑移式和倾倒式为主。 （3）随着地震波周期的增大，加速度放大系数极值将逐渐减小；速度和水平位移极值随着周期的增大而增大，当周期达到一定值后水平位移极值开始减小。地震波振幅对边坡动力响应分布规律影响较小，振幅的增减基本不改变边坡的加速度、速度和位移分布形式，但三者的极值随着地震波振幅的增加逐渐增大。 （4）地震荷载作用下边坡动力响应程度为凹形直线形凸形，边坡失稳多发育于对地震波有显著放大效应的部位。当坡高小于400m时，边坡加速度放大系数、速度和水平位移值均从坡脚至坡顶呈线性逐渐增大，三者的极值随着坡高的增大而增大；当坡高大于400m时，边坡加速度放大系数、速度和水平位移值从坡脚至坡顶呈非线性变化，具体表现为先增大后减小再增大的循环变化规律。边坡地震动力响应程度与坡度不存在明显的线性关系，坡度的改变不会引起边坡动力响应分布规律的变化，坡度为46～65°的边坡动力响应最为明显。 （5）老虎嘴崩塌模型系统不平衡力与输入地震波呈正相关关系，系统不平衡力经过一段时间的振动变化后最终趋于零；随着坡高的增加，加速度、速度放大系数逐渐减小，，并在坡顶位置有所增大，竖向加速度、速度放大系数整体大于水平方向；边坡位移主要集中于崩塌堆积体中后部及前缘坡脚位置；地震波对边坡应力分布影响较小，模型中最大主应力分布整体较均匀，其值随着深度的增大而增加，在基岩陡崖坡脚形成小范围的压应力和剪应力集中；堆积体前缘斜坡坡脚首先出现剪应变增量，然后向后缘扩展，最终在堆积体中后部基覆界面形成一条贯通的剪应变增量条带；堆积体中部分单元达到塑性状态，但未产生塑性破坏；老虎嘴崩塌边坡处于稳定状态。
[Abstract]:In the western canyon region of China, the problem of slope dynamic response is prominent. Wenchuan earthquake induced a large number of slope secondary disasters, aggravated the damage and losses in the earthquake area, and the aftershocks occurred frequently after the earthquake. Therefore, it is of great theoretical and practical significance to study the seismic dynamic response law of the slope in the earthquake area. This paper takes Yingxiu-Beichuan fault slope of Proterozoic magmatic rock in the epicenter of Wenchuan earthquake as the research object, based on the detailed field investigation data, using the methods of statistical analysis and numerical simulation analysis. The development law and influencing factors of slope geological hazard in this area are analyzed, and the influence of earthquake load and slope topographic condition on slope seismic dynamic response is further studied, and the case of Laohuzui collapse is taken as an example. The dynamic response law is simulated and analyzed. The results are as follows: 1) the study area belongs to the mid-high mountain canyon landform, the stratigraphic lithology is dominated by magmatic rock, the geological structure is complex, the seismic activity is frequent, and the valley strike intersects with the dominant joint direction at a large angle. (2) Middle-large scale collapses account for 90% of the geological hazards of the slope after the earthquake, mainly distributed linearly along the main stream of Minjiang River and its tributaries. The collapse of the right bank of the main stream is larger than that of the left bank in terms of density and scale (back slope effect), and the slope failure mode is mainly sliding and toppling. 3) with the increase of seismic wave period, the maximum value of acceleration magnification factor will gradually decrease. The maximum value of velocity and horizontal displacement increases with the increase of the period. When the period reaches a certain value, the extreme value of horizontal displacement begins to decrease. The amplitude of seismic wave has little effect on the distribution of slope dynamic response. The increase or decrease of amplitude does not change the distribution of acceleration, velocity and displacement of slope, but the extreme values of them increase with the increase of amplitude of seismic wave. 4) the dynamic response degree of slope under earthquake load is concave linear convex, and the slope instability is mostly developed in the position where the seismic wave is magnified significantly. When the slope height is less than 400m. The acceleration magnification factor, velocity and horizontal displacement of the slope increase linearly from the foot of the slope to the top of the slope, and the maximum values of the three increase with the increase of the height of the slope. When the slope height is greater than 400m, the acceleration magnification factor, velocity and horizontal displacement of the slope show nonlinear variation from the foot of the slope to the top of the slope. There is no obvious linear relationship between slope dynamic response and slope, and the change of slope will not cause the change of slope dynamic response distribution law. The dynamic response of the slope with a slope of 46 掳65 掳is the most obvious. 5) the unbalance force of the system is positively correlated with the input seismic wave, and the unbalance force of the system tends to zero after a period of vibration change. With the increase of slope height, the acceleration and velocity magnification coefficient decrease gradually, and increase at the top of the slope. The vertical acceleration, the velocity magnification factor is larger than the horizontal direction. The displacement of slope is mainly focused on the position of the back part and the foot of the front slope in the middle part of the collapse deposit. Seismic wave has little influence on slope stress distribution, and the maximum principal stress distribution in the model is uniform as a whole, and its value increases with the increase of depth, forming a small range of compressive stress and shear stress concentration at the base of steep slope of bedrock. At first, the shear strain increment appears at the slope foot of the front slope of the accumulation body, and then extends to the back edge, and finally a through shear strain increment strip is formed at the interface of the back base of the accumulation body. Some of the elements in the accumulated body reached the plastic state, but no plastic failure occurred. The slope of Tiger mouth collapse is in a stable state.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU45

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