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首页> 外文期刊>Journal of Applied Geophysics >Radar wave scattering loss in a densely packed discrete random medium: Numerical modeling of a box-of-boulders experiment in the Mie regime
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Radar wave scattering loss in a densely packed discrete random medium: Numerical modeling of a box-of-boulders experiment in the Mie regime

机译：密集堆积的离散随机介质中的雷达波散射损耗：Mie体制中的大块石块实验的数值模型

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摘要

In rough geologic media such as alluvial gravels, glacial tills, talus or colluvium, the grain sizes may span the range of GPR in situ wavelengths. Here we experimentally and numerically modeled the scattering loss from both rough-surface and subsurface dielectric scatterers. The combination of the selected radar frequency and the dimension of the scatterers placed the scattering within the Mie regime. We compared the GPR signal amplitude and waveform reflected from the metal sheet on the bottom of a large box filled with boulders with the numerically computed response from a discrete random medium (DRM) model. The DRM consists of a collection of densely packed ellipsoids. The size and orientation of the ellipsoids are randomized; the size has a Gaussian distribution similar to the physical experiment. The dielectric permittivity of the ellipsoids is constant and their electric conductivity is negligible. The starting in situ dominant pulse wavelength at 900. MHz was about 17. cm, as was about the average rock dimension. Experimentally, the 900-MHz radar pulse underwent most dispersion within the first in situ wavelength of depth, and then, at 500-700. MHz dominant frequency, the pulses underwent a near inverse range dependency loss rate, as if the media were a pure dielectric. The numerical model agrees well with the experimental data. Both experimental and numerical results support a significant scattering loss in Mie regime. Besides the scattering attenuation loss, velocity dispersion has also been observed from both observation and simulation. However, the scattering attenuation and dispersion cannot be fit by the Kramers-Kronig relation that is commonly found in intrinsic attenuation and worth further theoretical investigations.
机译：在粗糙的地质介质中，例如冲积碎石，冰川耕作，距骨或崩积层中，晶粒尺寸可能会跨越GPR的原位波长范围。在这里，我们通过实验和数值模拟来自粗糙表面和地下介质散射体的散射损耗。所选雷达频率和散射体尺寸的组合将散射置于Mie范围内。我们将GPR信号的振幅和从装满巨石的大盒子底部的金属板反射的波形与离散随机介质（DRM）模型的数值响应进行了比较。 DRM由密集堆积的椭球组成。椭球的大小和方向是随机的;大小具有类似于物理实验的高斯分布。椭圆体的介电常数是恒定的，并且其电导率可以忽略不计。 900. MHz处的起始原位主脉冲波长约为17厘米，约为平均岩石尺寸。在实验上，900 MHz雷达脉冲在深度的第一个原位波长内，然后在500-700内，经历了最大的色散。兆赫兹占主导地位的频率，脉冲经历了近乎相反的范围依赖性损耗率，就好像介质是纯电介质一样。数值模型与实验数据吻合良好。实验和数值结果均支持在Mie态下的显着散射损耗。除了散射衰减损失外，还通过观察和模拟观察到速度色散。但是，散射衰减和色散不能通过固有衰减中普遍存在的Kramers-Kronig关系来拟合，值得进一步的理论研究。

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