松散堰塞坝溃决的声发射响应试验研究

发布时间：2019-06-24 15:08

【摘要】：我国是一个自然灾害频发的国家,“5.12”地震后出现许多由地质灾害产生的松散堰塞坝,在大型的松散堰塞坝中约有一半是危险的。当遇上强降雨等条件,堰塞坝水位快速上涨,随时可能溃决,而串联形式的堰塞坝连续溃决产生的破坏性更强。在此背景下,论文首先分析研究了堰塞坝溃决模式和连续溃决的放大效应,其次选取七盘沟为研究对象进行室内物理模拟试验,借助声发射、微震、高速摄像机和孔压等仪器,探讨了不同坝体级配和不同泥浆容重情况下的溃决模式以及溃决过程中产生的声发射信号、震动信号、孔压信号和能量变化,最后进行堰塞坝连续溃决的室内物理模拟试验,定性的验证了串联堰塞坝破坏时释放能量的放大效应。用微震传感器记录堰塞坝溃决过程中震动的情况,记录震动加速度的变化历程。但通过时域波来了解震动的过程是比较麻烦的,HHT变换包含EMD分解和Hilbert变换,HHT是分析非线性、非平稳信号的一种新方法。通过该变换得到频谱,进而在频域中进行分析,通过该变换也可以清楚的刻画震动中时频能量的分布。通过孔隙水压力剂和视频来分析堰塞坝溃决过程中土体内部有效应力的变化。借助声发射仪器来测定不同工况条件下堰塞坝溃决产生的能量,声发射数据主要从振铃计数、能量、幅值、累计能量四个方面进行分析。振铃计数可以表现出声发射的活动性,其幅值越大密度越大,声发射活动性越强。幅值也称为幅度,该指标不受门限的影响,直接决定声发射的可测性,间接表现声发射信号的强度和某段时间的某个事件。能量反映事件的相对能量或者相对强度,主要用于不同条件下的对比。累计能量是指在整个堰塞坝破坏过程中产生的能量之和,累积曲线的曲率也可以反应某段时间的特定事件,是一个相对指标。通过室内物理模拟试验并借助不同仪器,论文得出如下结论:(1)松散堰塞坝溃决过程中泥流渗透、土体细颗粒运移以及坝体部分坍塌都会产生声发射现象,声发射信号的幅值、振铃计数和累计能量与坝体细粒含量和泥浆容重都有密切关系。(2)不同坝体细粒含量和不同泥浆容重情况下,堰塞坝溃决的模式大部分为漫顶溃决,但细粒含量很少的松散堰塞坝由于静水压力的作用可能发生滑坡破坏。漫顶溃决过程中,坝体背水坡面首先形成多条细小冲沟,随着冲刷加剧,冲沟两侧土体坍塌形成较大冲沟和溃口,冲沟掏蚀坝体背水坡面中部并冲刷坝脚形成冲坑,溃口的下切和侵蚀加剧将使坝体一侧出现较大的矩形溃槽,此时坝前水位快速下降,直至最终破坏。(3)泥流在坝体土体中的渗透性和堰塞坝的溃决过程影响着孔隙水压力的变化。孔隙水压力在坝体中的变化大致分为三种情况:一种是孔压在一段时间内持续增加,随着坝体溃决孔压消散;另一种是孔压前期增加并不明显或者增加幅值很小,在坝体溃决瞬间激增,而后随着坝体破坏而消散;最后一种是孔压持续增长了一段时间,在坝体溃决瞬间激增,随着坝体破坏而消散。坝体的细粒含量和泥浆的容重影响着泥流在坝体土体中的渗透性,漫顶溃决中冲沟、溃口和冲槽的位置影响着泥浆在坝体中的渗透路径,进而影响孔压值。(4)借助微震传感器和声发射传感器得出了不同坝体细粒含量和不同泥浆容重情况下堰塞坝破坏时产生的能量,认为溃决时长、溃口和溃槽的形成与扩展以及溃决过程中的坍塌直接影响着溃决过程中产生能量的大小。溃口和溃槽的形成与扩展以及堰塞坝土体的坍塌,对应能量曲线中曲率的变化点。(5)通过进行堰塞坝连续溃决的室内物理模拟试验,得出串联堰塞坝破坏时产生的能量会有一个放大效用,虽然不同条件下放大系数不同,但可以定性的得出结论。
[Abstract]:China is a country with frequent natural disasters. After the "5.12" of the earthquake, a lot of loose weir dam, which are caused by the geological disasters, are in danger in about half of the large-scale loose weir dam. When the condition of strong rainfall is encountered, the water level of the weir dam is rising rapidly, which may be broken at any time, and the continuous collapse of the dam-type dam in the series form is more destructive. In this background, the paper first analyzes the amplification effect of the dam break mode and the continuous collapse, and then selects the seven-disk ditch as the research object to carry out the indoor physical simulation test, by means of acoustic emission, micro-shock, high-speed camera and hole pressure, etc. In this paper, the burst mode and the acoustic emission signal, the vibration signal, the pore pressure signal and the energy change of different dam body gradation and different mud weight density are discussed, and the indoor physical simulation test of the continuous collapse of the weir dam is carried out. The amplification effect of the release energy during the failure of the series weir dam is qualitatively verified. The change course of the vibration acceleration is recorded by using the micro-vibration sensor to record the vibration in the dam break process. But it is difficult to know the process of vibration by time-domain wave. The HHT transform includes EMD and Hilbert transform, and HHT is a new method for analyzing non-linear and non-stationary signals. The frequency spectrum is obtained by the transformation, and then the analysis is carried out in the frequency domain, and the distribution of time-frequency energy in the vibration can be clearly depicted by the transformation. The change of the effective stress in the soil during the dam-breaking process is analyzed by the pore water pressure and the video. In this paper, the energy and acoustic emission data generated by the dam break in different working conditions are measured by means of an acoustic emission instrument, and the acoustic emission data is mainly analyzed from the four aspects of ringing count, energy, amplitude and accumulated energy. The ringing count can show the activity of the sound emission, and the greater the amplitude, the stronger the acoustic emission activity. The amplitude is also referred to as the amplitude, which is not affected by the threshold, directly determines the measurability of the acoustic emission, and indirectly expresses the intensity of the acoustic emission signal and an event of a certain period of time. The energy reflects the relative energy or relative strength of the event, mainly for comparison under different conditions. The accumulated energy refers to the sum of the energy generated during the whole dam failure process, and the curvature of the accumulated curve can also reflect the specific events of a certain period of time, which is a relative index. Through the indoor physical simulation test and by means of different instruments, the following conclusions are drawn: (1) The seepage of the mud, the migration of the fine particles of the soil and the collapse of the part of the dam body can produce the acoustic emission phenomenon, the amplitude of the acoustic emission signal, The ringing count and the accumulated energy are closely related to the particle content of the dam body and the volume weight of the mud. (2) In the case of the fine particle content of different dam bodies and the volume weight of different mud, most of the modes of the dam break of the weir dam are overtopping, but the loose weir dam with little fine particle content may be damaged due to the effect of the hydrostatic pressure. in the process of overtopping, a plurality of fine gullies are formed on the back surface of the dam body, The lower cutting and erosion of the break will cause a large rectangular trough to appear on one side of the dam body, and the water level in front of the dam will drop rapidly until the end of the dam is finally broken. (3) The permeability of the mud flow in the body of the dam body and the collapse process of the weir dam affect the change of pore water pressure. The change of pore water pressure in the dam body is generally divided into three cases: one is that the pore pressure is continuously increased for a period of time, and the pore pressure of the dam body is dissipated; the other is that the initial increase of the pore pressure is not obvious or the amplitude is small, and at the moment of the dam break, And then, with the destruction of the dam body, the last one is that the pore pressure has been continuously increased for a period of time, and the sudden increase of the dam break in the dam body will be dissipated with the destruction of the dam body. The particle content of the dam body and the volume weight of the mud affect the permeability of the mud flow in the soil body of the dam body, and the position of the gullies, the break and the scour groove in the overtopping is affected by the seepage path of the mud in the dam body, and further the pore pressure value is affected. and (4) using the micro-shock sensor and the acoustic emission sensor to obtain the energy generated during the failure of the dam plug dam under the condition of the fine particle content of different dam bodies and the volume weight of different mud, The formation and expansion of the break and the collapse and the collapse of the collapse directly affect the magnitude of the energy produced during the break-up process. The formation and expansion of the break and the trough and the collapse of the dam body mass correspond to the change point of the curvature in the energy curve. (5) Through the indoor physical simulation test of the continuous collapse of the weir dam, it is concluded that the energy produced in the failure of the series weir dam is an amplification effect, although the amplification factor is different under different conditions, it can be concluded qualitatively.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV122.4;TV698.237

【参考文献】