Analysis of bender element test interpretation using the discrete element method
Analysis of bender element test interpretation using the discrete element method
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DOI：
10.1007/s10035-015-0552-6
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发表时间：
2015-03
期刊：
影响因子：
2.4
通讯作者：
J. O’Donovan;Catherine O'Sullivan;G. Marketos;D. M. Wood
中科院分区：
文献类型：
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作者：
J. O’Donovan;Catherine O'Sullivan;G. Marketos;D. M. Wood
虽然弯曲元件测试作为一种确定土壤硬度的实验室技术现在已经很成熟，但解释数据的可靠技术仍然难以捉摸。建立了均匀球面中心立方堆积的离散元模型，模拟了弯曲单元试验，从根本上研究了这一试验。在DEM模拟期间，与实验室测试中提供的数据类似，记录了发射器和接收器信号，并用颗粒尺度测量(力、应力和位移)补充了这些宏观尺度数据。以前在实验和数值研究中采用的一系列方法被用来在时间域和频率域分析所产生的数据。这些方法的不足之处从剪切刚度值的差异和这些值的频率依赖性中可见一斑。粒子尺度的数据能够可视化波通过样品的过程，而且发现不可能精确地将横波到达接收器的情况与先前提出的沿接收器记录的信号的任何特征点联系起来。通过将二维快速傅立叶变换(2DFFT)应用于描述位于发射器和接收器元件之间的粒子速度的数据，获得了最可靠的剪切波速度确定。DEM模型和这种二维FFT方法的使用有助于建立系统响应对粒间力-位移定律(接触模型)微小变化的敏感性。
While bender element testing is now well-established as a laboratory technique to determine soil stiffness, a robust technique to interpret the data remains elusive. A discrete element method (DEM) model of a face-centred cubic packing of uniform spheres was created to simulate bender element tests to investigate this test from a fundamental perspective. During the DEM simulations transmitter and receiver signals were recorded, analogous to the data available in laboratory tests, and these macro-scale data were supplemented with particle scale measurements (forces, stresses and displacements). A range of approaches previously applied in experimental and numerical studies were used to analyse the resulting data in both the time and frequency domains. The shortcomings in these approaches are clear from the differences in the resultant shear stiffness values and the frequency-dependent nature of the values. The particle-scale data enabled visualization of the passage of the wave through the sample, and it was found not to be possible to precisely link the arrival of the shear wave at the receiver and any of the previously proposed characteristic points along the signal recorded at the receiver. The most reliable determination of the shear wave velocity was obtained by applying a two-dimensional fast Fourier transform (2D FFT) to the data describing the velocity of the particles lying between the transmitter and receiver elements. Use of the DEM model and this 2D FFT approach facilitated the sensitivity of the system response to small variations in the interparticle force–displacement law (the contact model) to be established.