瑞利面波检测混凝土裂缝的方法研究

发布时间：2018-05-13 05:30

本文选题：瑞利面波勘探 + 裂缝检测　；参考：《长江大学》2014年硕士论文

【摘要】：改革开放以来,随着国家加大基础设施建设的投入力度,各类大型工程建筑不断涌现,由于现代工程建筑的主要材料是钢筋混凝土,而混凝土由于受到各种内部或外部作用的影响而产生裂缝,进而影响混凝土的质量,对建筑物造成很大的危害。因此必须对这些裂缝进行检测,掌握裂缝状况及有关参数,以判断裂缝对建筑物的危害程度及研究相应的补强措施,挽救人民的生命财产安全。混凝土裂缝检测一直是工程建设中的技术难题。由于检测理论和方法的不足,目前,对深度大的垂直裂缝还没有一种有效的检测方法。为了合理评价裂缝对混凝土结构安全性的影响和制定后续的加固方案,必须准确确定裂缝的状态、发展趋势和形成原因。其中以裂缝的深度、长度和宽度作为最重要的三个指标。尤其裂缝深度是其中的关键指标。在实际检测工作中,裂缝深度检测要比长度和宽度的检测困难得多。裂缝宽度检测分三类：塞尺或裂缝宽度对比卡(用于粗测,精度低)、裂缝显微镜(精度在0.02～0.05mm)、裂缝宽度测试仪。目前最主要的方法还是裂缝显微镜,但裂缝宽度测试仪发明后,避免了人工近距离调节焦距的要求,降低了劳动强度。裂缝深度检测最直接和准确的方法是钻孔取样,但该方法不仅费时费力,而且对建筑结构有一定的损害,当裂缝深度较大或位于特殊部位时,难以进行钻孔取样。其次是声波对测法,在平行裂缝的一侧激发声波信号,另一侧接收透射的信号,通过比较无裂缝和有裂缝的透射信号或通过透射层析成像来判断裂缝深度,然而此法很多时候需要在裂缝两侧钻孔来布置观测系统,同样也是有损检测。目前更多采用的是无损检测技术,主要有超声波法和冲击弹性波法,这两种方法都是在混凝土表面布置观测系统,根据裂缝底端的折射信号的特征和传播路径的几何关系来推算裂缝的深度。超声波法通过超声波探头激发和接收信号,超声信号的频率高但能量较低,一般适用于浅裂缝的检测。冲击弹性波法采用锤击震源,信号频率低但能量高,适用于较深裂缝的检测。但这两种方法存在的问题是当裂缝中存在填充物时,声波信号大部分能量通过填充物传递,裂缝底端的折射信号往往很难判断,对深裂缝尤其显著。近年来,发展一种新的裂缝无损检测方法-瑞利面波法,同样在混凝土表面布置观测系统,采用锤击震源,通过接收的瑞利面波特征来推算裂缝的深度。超声波法和冲击弹性波法是利用弹性波中的体波进行检测,而地表激发的弹性波中大部分能量为瑞利面波,且在分层介质中,瑞利面波具有频散特性,瑞利面波的波长不同,穿透深度也不同。瑞利面波法具有分辨率高、应用范围广、受场地影响小、检测设备简单、检测速度快、经济等一系列优点,广泛应用于浅表层岩土工程勘察和灾害地质调查等领域。本文简要回顾了各种传统物探方法在裂缝检测中的应用以及运用瑞利面波对裂缝进行无损检测的事例。引出研究课题-运用瑞利面波检测混凝土的垂直裂缝。在瑞利面波原理介绍部分详细介绍了如何运用凡友华的无量纲实数传递矩阵算法对频散曲线进行正演计算,通过交错网格有限差分法以及Rune Mittet的自由边界条件处理和指数衰减吸收边界条件处理进行数值模拟。运用τ-p变换算法对频散曲线能量谱进行计算。把模拟后得到的频散曲线值与实际理论值作对比。得到此数值模拟方法的可行性。之后进行裂缝介质的数值模拟,分别建立有裂缝与无裂缝的模拟进行研究对比,以及建立不同深度的裂缝进行研究对比,最后把我们建立的垂直裂缝数值模拟与三峡大坝实测数据作对比。发现体波和面波通过裂缝时都会产生反射和透射,反射波比透射波的能量要强,并且都会沿裂缝向下传播,在裂缝端点处产生散射。而且发现在裂缝介质中,面波没有高阶模。需要注意的是如果裂缝是空气的话,面波和纵波都会有反射和散射,但不会有透射。意味着在实际检测中,裂缝的一侧只会接收到散射波。然而瑞利面波检测混凝土垂直裂缝的理论尚不完善,还有待广大面波工作者进一步的研究。
[Abstract]:Since the reform and opening up, as the state has increased the investment in infrastructure construction, all kinds of large-scale engineering buildings are constantly emerging, because the main material of the modern engineering construction is reinforced concrete, and the concrete is caused by the effects of various internal or external effects, which affect the quality of the concrete and cause a great deal of construction. Therefore, it is necessary to test the cracks, grasp the conditions of the cracks and the related parameters, in order to judge the extent of the damage to the building and to study the corresponding reinforcement measures to save the people's life and property safety.
Concrete crack detection has always been a technical problem in engineering construction. Due to the lack of detection theory and method, there is no effective detection method for deep vertical cracks at present. In order to evaluate the effect of cracks on the safety of concrete structure and formulate a subsequent consolidation scheme, it is necessary to determine the state of the crack accurately. The depth, length and width of the cracks are the three most important indicators. Especially the depth of the crack is the key index. In the actual testing, the detection of the depth of the crack is much more difficult than the length and width.
Crack width detection is divided into three categories: tape gauge or crack width contrast card (used for coarse measurement, low precision), fracture microscope (precision in 0.02 to 0.05mm), crack width tester. The most important method is crack microscope at present, but after the invention of crack width tester, it avoids the requirement of the close range adjustment focal length and reduces the labor intensity.
The most direct and accurate method for detecting crack depth is drilling sampling, but the method is not only time-consuming and hard to take, but also has certain damage to the structure of the building. When the depth of the crack is large or in the special part, it is difficult to carry out the drilling sampling. Secondly, the acoustic wave is used to measure the sound wave signal on one side of the parallel crack and the other side receives the transmission letter. The fracture depth is judged by comparing transmission signals without cracks and cracks or through transmission tomography. However, this method needs to be drilled on both sides of the crack to arrange the observation system in many cases, and it is also a damage detection.
At present, more use is nondestructive testing technology, mainly ultrasonic wave method and shock elastic wave method. These two methods all arrange observation system on the surface of concrete. According to the characteristics of the refraction signal at the bottom of the crack and the geometric relation of the propagation path, the ultrasonic wave method excite and receive the signal through the ultrasonic probe. Sound signals have high frequency but low energy, which are generally applicable to the detection of shallow cracks. Shock elastic wave method adopts a hammer shock source, which is low in frequency but high in energy, and is suitable for detection of deep cracks. However, the problem of these two methods is that when there are fillers in the crack, most of the energy of acoustic signals is passed through the filling material and the end of the crack is at the end of the crack. Refraction signals are often difficult to judge, especially for deep fractures.
In recent years, a new nondestructive testing method, Rayleigh surface wave method, is developed, which is also arranged on the surface of concrete. By hammering the source, the depth of the crack is calculated by the characteristics of the Rayleigh wave received. The ultrasonic wave method and the impact elastic wave method are detected by the body wave in the elastic wave, while the elastic wave excited by the surface is large. Partial energy is Rayleigh surface wave, and in stratified medium, Rayleigh surface wave has frequency dispersion characteristics, Rayleigh surface wave has different wavelengths and penetration depth. Rayleigh surface wave method has a series of advantages, such as high resolution, wide application range, small influence of site, simple detection equipment, rapid detection speed, and a series of advantages, which are widely used in shallow surface geotechnical engineering exploration. Inspection and disaster geological survey and other fields.
This paper briefly reviews the application of various traditional geophysical methods to crack detection and the application of Rayleigh surface wave to nondestructive testing of cracks. The research topic - the use of Rayleigh surface wave to detect the vertical cracks in concrete. The application of van Eila's dimensionless real number transfer moment in the Rayleigh wave principle is introduced in detail. The dispersion curve is forward calculated by the array algorithm, and the numerical simulation is carried out by the staggered grid finite difference method, the free boundary condition treatment of Rune Mittet and the exponential attenuation absorption boundary condition. The energy spectrum of the dispersion curve is calculated by the algorithm of the tau -p transformation. The calculated dispersion curve values are compared with the actual theoretical values. The numerical simulation of the fractured medium is carried out after the numerical simulation of the fractured medium, the comparison of the crack and the non crack simulation, and the comparison of the cracks in different depths are compared. Finally, the numerical simulation of vertical cracks and the measured data of the Three Gorges dam are compared. The surface waves are reflected and transmitted through cracks. The energy of the reflected Bobbi transmission wave is strong, and it will propagate down the crack and scatter at the end of the crack. And it is found that there is no high order mode in the fractured medium. It is important to note that if the crack is air, both the surface wave and the longitudinal wave will reflect and scatter, but not the surface wave and the longitudinal wave, but not the surface wave and the longitudinal wave. There is transmission. It means that in actual detection, only the scattering waves will be received on one side of the crack. However, the theory of vertical crack detection of concrete by Rayleigh surface wave is not perfect, and it is still to be further studied by the broad face wave workers.

【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU755.7

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