Vajont滑坡稳定性及高速运动特征的DDA模拟研究

发布时间：2018-01-22 05:03

本文关键词： Vajont滑坡 DDA 稳定性高速运动强度衰减　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：大型滑坡,由于体积庞大,能以极高的运动速度向前滑移,通常会给沿途民居聚居地带来毁灭性的灾难。发生在意大利的Vajont滑坡,是大型高速滑坡中的典型,引起了大型高速滑坡的研究热潮。Vajont滑坡从开始溃滑到完全停积,历时不足1分钟,最大滑移速度达到了惊人的20m/s～30m/s,冲向水库的岩石滑体激起了约平均100m高的涌浪,淹没了下游五个村镇,2000多人因为此次灾难失去了生命。目前针对Vajont滑坡的数值方法研究中,存在岩体参数取值不统一的问题。另外,滑带摩阻力降低被认为是导致滑坡高速运动的原因,现阶段研究多为探讨滑带强度衰减对滑坡运动能力的影响,而对于滑体强度衰减引起滑坡运动能力改变的研究较为缺乏。本文以Vajont滑坡为例,针对上述问题,利用DDA方法分析了 Vajont滑坡在稳定阶段及运动阶段的特征,根据滑坡特征反演探讨了强度衰减对滑坡运动能力的影响,得出如下结论:(1)基于位移突变准则建立了一种求解斜坡临界态强度的方法,经与传统强度折减法验证,证实了其可靠性。具体在本文计算中,即在程序中每隔固定步数对滑面初始强度自动进行一次折减,当斜坡特征点位移发生突变时,对应的强度即为临界强度。(2)节理岩体摩擦角、滑面粘聚力和静水位高度等对斜坡稳定状态的影响较大。节理岩体摩擦角每升高5°,维持斜坡稳定的滑面临界摩擦角则相应减小0.5°;当水库水位升高至计划最高蓄水高度时,斜坡的安全系数约降低了 11.9%,由于降雨等导致斜坡内部水位线非水平分布时,斜坡的安全性有一定程度的降低;滑面粘聚力只有达到与法向应力同一量级,对稳定性的影响则变得较为明显,考虑到Vajont滑坡滑面区为粘土夹层,粘聚力较小,因此稳定性分析时,将粘聚力作用等价转化为摩擦角作用或不考虑。(3)当Vajont滑坡沿着完整滑裂面启动时,滑面及滑体的强度都有相当程度的降低,这是造成滑坡加速高速下滑的原因。同样程度的衰减,滑坡运动距离对滑带强度的降低,表现的更加敏感,而滑体强度的变化是在此基础上促进了滑坡前缘块体的爬升能力。
[Abstract]:Large landslides, which can slip forward at a very high speed because of their large size, usually bring devastating disasters to settlements along the way. The Vajont landslide occurred in Italy. Vajont landslide is typical of large high speed landslide, which caused the research upsurge of large high speed landslide .Vajont landslide from the beginning to complete collapse to stop production, which lasted less than 1 minute. The maximum slip rate reached an astonishing 20 m / s / s, and the rock slide that rushed towards the reservoir caused a surge of about 100 m high, flooding five villages and towns downstream. More than 2 000 people lost their lives as a result of the disaster. In the current numerical study of Vajont landslide, there is a problem that the parameters of rock mass are not uniform. The reduction of sliding zone friction is considered to be the cause of landslide high speed movement. At this stage, most of the research is to discuss the influence of slip zone strength attenuation on landslide movement ability. However, the study of landslide movement ability caused by strength attenuation of sliding body is relatively scarce. This paper takes Vajont landslide as an example, aiming at the above problems. The characteristics of Vajont landslide in the stable stage and the movement stage are analyzed by using DDA method, and the influence of intensity attenuation on the landslide movement ability is discussed according to the inversion of landslide characteristics. The conclusion is as follows: 1) based on the displacement catastrophe criterion, a method for calculating the critical strength of slope is established, which is verified by the traditional strength reduction method. In the program, the initial strength of sliding surface is automatically reduced once every fixed number of steps. When the displacement of slope characteristic point changes, the corresponding strength is critical strength. 2) the friction angle of jointed rock mass. The cohesive force of sliding surface and the height of static water level have great influence on the stable state of slope. The friction angle of jointed rock mass increases by 5 掳, and the friction angle of sliding face to boundary decreases by 0.5 掳for maintaining slope stability. When the water level of the reservoir rises to the planned maximum water storage height, the slope safety factor decreases by 11.9. due to rainfall and other factors, the water level of the slope is not horizontal distribution. The slope safety is reduced to a certain extent; The cohesive force of sliding surface is only the same as normal stress, and the influence on stability becomes more obvious. Considering that the slip surface area of Vajont landslide is clay intercalation, the cohesion force is small, so the stability analysis. When the Vajont landslide starts along the whole slip surface, the strength of the sliding surface and the sliding body will be reduced to a certain extent. This is the cause of the landslide to accelerate the high-speed slide. The same degree of attenuation, landslide distance to reduce the strength of the slide zone, performance is more sensitive. On the basis of the change of slide strength, the climbing ability of landslide front block is promoted.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.22

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