圆柱形击实试件的剪切波传播特性及其波速测试方法研究

发布时间：2018-06-09 13:55

本文选题：剪切波 + 弹性波理论　；参考：《重庆交通大学》2015年硕士论文

【摘要】：剪切波波速是描述土体工程性质的一项重要指标,能很好地反映岩土的动力学特性,在工程建设中应用广泛。目前,测试土体剪切波速度的方法主要有两种:原位测试法和室内测试法。前者能获得工程土体实际的剪切波传播速度,但其测试成本高、操作繁杂,能考虑的条件较为单一,且试验结果的适用范围较窄。室内测试法操作较为简单,可以进行参数化研究,并可以考虑不同的试验条件。但该方法常会受到剪切波换能器、试样尺寸、测试位置等因素的影响,从而难以获得土体的真实剪切波速值,阻碍了该方法在工程中的应用。鉴于此,本文依托于国家自然科学基金项目—基于三维波电场耦合全息成像的堤坝隐患诊断技术研究(51279219),基于发明专利—一种室内击实试件的横波波速测试方法(201210075217X)和弹性波传播理论,提出圆柱形击实试件的剪切波传播特性及其波速测试方法研究。本文的主要研究内容和结论如下:(1)基于弹性波传播理论,建立了分析弹性波在圆柱形击实试件中传播的三维有限元模型。基于该模型,分别计算了在不同加载频率、不同加载激励大小以及不同尺寸条件下模型中的波动。(2)基于有限元计算结果,分析了加载频率、加载激励大小以及模型尺寸对剪切波传播的影响规律。结果表明,模型中的剪切波速度和波能衰减均随着加载频率的增大而增大,但总体来说,加载频率对剪切波传播的影响程度不大;瞬时激励大小对剪切波速度基本没有影响;直径0.2m是剪切波速度发生明显变化的转折点。若超过该直径,增大直径对剪切波速度的影响很小;若小于该直径,即使直径变化很小,剪切波速度也将明显增大,而且剪切波速度随着直径的改变几乎是呈线性变化。(3)基于专利—一种室内击实试件的横波波速测试方法,制作不同干密度的击实试件并测试各试件中的剪切波速度,得到剪切波速度与干密度之间近似呈线性关系。采用超声波检测法测试了各击实试件的纵波速度,得到纵波速度与干密度近似呈线性关系。根据测试结果计算了土的弹性参数并进行了分析。(4)综合数值模拟分析以及实测结果,对实测剪切波速度进行了修正,并提出了修正后的剪切波速度测试方法。
[Abstract]:Shear wave velocity is an important index to describe the engineering properties of soil, which can well reflect the dynamic characteristics of rock and soil, and is widely used in engineering construction. At present, there are two main methods for measuring the shear wave velocity of soil: in situ and in-house. The former can obtain the actual shear wave propagation velocity of engineering soil, but its testing cost is high, the operation is complicated, the conditions can be considered are relatively simple, and the application range of the test results is relatively narrow. The indoor test method is easy to operate and can be parameterized and different test conditions can be considered. However, the method is often affected by the shear wave transducer, sample size, testing position and other factors, so it is difficult to obtain the true shear wave velocity of soil, which hinders the application of the method in engineering. In view of this, This paper is based on the project of National Natural Science Foundation of China-based on 3D wave electric field coupled holographic imaging, the research on hidden hazard diagnosis technology of embankment and dam. Based on the invention patent, a method of measuring the velocity of shear wave and elastic wave propagation theory. The characteristics of shear wave propagation and the measurement method of wave velocity of cylindrical compacted specimens are presented. The main contents and conclusions of this paper are as follows: (1) based on the theory of elastic wave propagation, a three-dimensional finite element model is established to analyze the propagation of elastic wave in cylindrical compacted specimens. Based on the model, the fluctuation of the model under different loading frequency, different load excitation size and different size is calculated, and the loading frequency is analyzed based on the results of finite element calculation. The effect of loading excitation and model size on shear wave propagation. The results show that the shear wave velocity and wave energy decay in the model increase with the increase of loading frequency, but in general, the influence of loading frequency on shear wave propagation is not significant, but the instantaneous excitation has no effect on shear wave velocity. The diameter of 0.2m is the turning point when the velocity of shear wave changes obviously. If the diameter exceeds the diameter, the increase of the diameter has little effect on the velocity of the shear wave, and if the diameter is smaller than the diameter, the velocity of the shear wave will increase obviously even if the diameter changes very little. And the shear wave velocity is almost linearly varying with the diameter.) based on the patent, a method for measuring the shear wave velocity of the compacted specimens in laboratory, we make the compacted specimens with different dry densities and test the shear wave velocities in each specimen. The approximate linear relationship between shear wave velocity and dry density is obtained. The longitudinal wave velocities of the compacted specimens were measured by ultrasonic method, and the linear relationship between the longitudinal wave velocities and dry density was obtained. According to the test results, the elastic parameters of the soil are calculated and analyzed. 4) the numerical simulation analysis and the measured results are carried out. The measured shear wave velocity is corrected and the modified shear wave velocity measurement method is put forward.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411

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