非均匀地质介质的电磁波频散实验研究
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摘要
宽频带电磁波在地质介质传播时会发生频散。频散效应,对宽带电磁波勘探既是干扰,也是可资利用的信息。本文采用物理实验的方法研究不同介质的频散效应,以期为频散效应的利用提供实践基础。论文的主要内容与成果如下:
1.物理模型实验研究
以NI公司的高频信号发射与采集硬、软件为核心,搭建了一个宽带(100KHz--2.8GHz)波动信号采集分析系统;用连续排列的43个水泥块和3个铸铁块分别模拟高阻介质和低阻介质,模型块的尺度为100cm×10cm×50cm;在模型上方55cm处发射、接收电磁波,实验测定了各模型在无覆盖和15cm厚水层覆盖情况下对0.5 GHz,1.0 GHz,1.5 GHz电磁波的反射强度。通过对测量结果的计算分析,获得了如下认识:
(1)在无水层覆盖时,水泥模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度减少了51.98%,反射振幅频散率为1.0396/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度减少了41.97%,反射振幅频散率0.8394/GHz,反射振幅的频散呈非线性变化。铸铁模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度减少了43.73%,反射振幅频散率为0.8746/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度减少了了38.55%,反射振幅频散率为0.7710/GHz,反射振幅的频散也呈非线性变化。在测量的频段内,低阻铸铁模块的频散幅度小于高阻水泥模块的频散,但随频率的增加,反射强度的衰减相对较缓。
(2)在有水层覆盖时,水泥模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度减少了59.92%,反射振幅频散率为1.1984/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度了减少38.91%,反射振幅频散率为0.7782/GHz。铸铁模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度了减少48.79%,反射振幅频散率为0.9758/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度减少了31.79%,反射振幅频散率为0.6358/GHz。水覆盖层的存在,提高了低频段的频散幅度,但减小了高频段的频散幅度。
2.现场物理模型实验研究
使用TerraSIRch SIR-3000地质雷达系统,用0.1GHz,0.4 GHz,0.9 GHz三个频率测量在土壤中埋深100cm的铸铁管的反射强度。
通过计算,铸铁管对0.4GHz电磁波的反射强度相对于0.1GHz的反射强度减少了0.1423%,反射振幅频散率为0.004745/GHz;0.9GHz电磁波的反射强度相对于0.4GHz的反射强度减少了0.4487%,反射振幅频散率为0.008974/GHz,反射振幅的频散呈非线性变化,随频率的增加,反射强度的衰减加快。
The process of wideband electromagnetic wave propagation in geologic mediums occur frequency-dispersion phenomenon. Frequency-dispersion phenomenon is not only disadvantage but also advantage. By physical experiment studying on frequency-dispersion response of wideband electromagnetic wave over different medium in the thesis, it offers practical experience in using frequency-dispersion phenomenon. The main achievements of the thesis are as follows:
1. Physical model experiment studying indoor
Construct wideband (100KHz--2.8GHz) electromagnetic wave signal analyzing system base on NI company's key hardware and software of high frequency signal transmitting and receiving. Simulate high resistance medium by forty-three concrete modules (100cmxl0cmx50cm) continuously arranged and low resistance medium by three cast iron modules (same scale). Transmit and receive electromagnetic wave at the height of 55cm over the model. Measure each module reflective intensity of 0.5GHz, 1.0GHz, 1.5GHz electromagnetic wave in the condition of non-overcast and overcast water layer of 15 cm thickness. By analyzing and computing observe data, the main conclusion of the experiment indoor are as follows:
(1) On non-overcast water layer, for concrete modules, reflective intensity of frequency 1.0GHz is less 51.98% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 1.0396/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 41.97% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.8394/GHz between 1.5GHz and 1.0GHz . Concrete modules' frequency-dispersion of reflective amplitude variety non-linear . For cast iron modules, reflective intensity of frequency 1.0GHz is less 43.73% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 0.8746/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 38.55% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.7710/GHz between 1.5GHz and 1.0GHz . Cast iron modules' frequency-dispersion of reflective amplitude variety non-linear, too. Low resistance cast iron modules' the value of frequency-dispersion is less than high resistance concrete modules' in the same frequency difference. The attenuation of reflective intensity become weaker in the high frequency band than in low frequency band.
(2) On overcast water layer, for concrete modules, reflective intensity of frequency 1.0GHz is less 59.92% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 1.1984/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 38.91% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.7782/GHz between 1.5GHz and 1.0GHz . For cast iron modules, reflective intensity of frequency 1.0GHz is less 48.79% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 0.9758/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 31.79% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.6358/GHz between 1.5GHz and 1.0GHz . Because of the overcast water layer, the value of frequency-dispersion in the low frequency band become stronger, however, the value of frequency-dispersion in the high frequency band become weaker.
2. Physical model experiment studying local
Measure the different frequency of 0.1 GHz, 0.4 GHz, 0.9 GHz reflective intensity of the cast iron pipe embodied in soil of 100 cm depth by TerraSIRch SIR-3000 Ground Probe Radar system.
By analyzing and computing observe data, for cast iron pipe, reflective intensity of frequency 0.4GHz is less 0.1423% than reflective intensity of frequency 0.1GHz, and reflective amplitude frequency-dispersion rate is 0.004745/GHz between 0.4GHz and 0.1GHz ; reflective intensity of frequency 0.9GHz is less 0.4487% than reflective intensity of frequency 0.4GHz, and reflective amplitude frequency-dispersion rate is 0.008974/GHz between 0.9GHz and 0.4GHz . Cast iron pipe frequency-dispersion of reflective amplitude variety non-linear, and The attenuation of reflective intensity become stronger in the high frequency band than in low frequency band.
1.物理模型实验研究
以NI公司的高频信号发射与采集硬、软件为核心,搭建了一个宽带(100KHz--2.8GHz)波动信号采集分析系统;用连续排列的43个水泥块和3个铸铁块分别模拟高阻介质和低阻介质,模型块的尺度为100cm×10cm×50cm;在模型上方55cm处发射、接收电磁波,实验测定了各模型在无覆盖和15cm厚水层覆盖情况下对0.5 GHz,1.0 GHz,1.5 GHz电磁波的反射强度。通过对测量结果的计算分析,获得了如下认识:
(1)在无水层覆盖时,水泥模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度减少了51.98%,反射振幅频散率为1.0396/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度减少了41.97%,反射振幅频散率0.8394/GHz,反射振幅的频散呈非线性变化。铸铁模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度减少了43.73%,反射振幅频散率为0.8746/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度减少了了38.55%,反射振幅频散率为0.7710/GHz,反射振幅的频散也呈非线性变化。在测量的频段内,低阻铸铁模块的频散幅度小于高阻水泥模块的频散,但随频率的增加,反射强度的衰减相对较缓。
(2)在有水层覆盖时,水泥模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度减少了59.92%,反射振幅频散率为1.1984/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度了减少38.91%,反射振幅频散率为0.7782/GHz。铸铁模块对1.0GHz电磁波的反射强度相对于0.5GHz的反射强度了减少48.79%,反射振幅频散率为0.9758/GHz;1.5GHz电磁波的反射强度相对于1.0GHz的反射强度减少了31.79%,反射振幅频散率为0.6358/GHz。水覆盖层的存在,提高了低频段的频散幅度,但减小了高频段的频散幅度。
2.现场物理模型实验研究
使用TerraSIRch SIR-3000地质雷达系统,用0.1GHz,0.4 GHz,0.9 GHz三个频率测量在土壤中埋深100cm的铸铁管的反射强度。
通过计算,铸铁管对0.4GHz电磁波的反射强度相对于0.1GHz的反射强度减少了0.1423%,反射振幅频散率为0.004745/GHz;0.9GHz电磁波的反射强度相对于0.4GHz的反射强度减少了0.4487%,反射振幅频散率为0.008974/GHz,反射振幅的频散呈非线性变化,随频率的增加,反射强度的衰减加快。
The process of wideband electromagnetic wave propagation in geologic mediums occur frequency-dispersion phenomenon. Frequency-dispersion phenomenon is not only disadvantage but also advantage. By physical experiment studying on frequency-dispersion response of wideband electromagnetic wave over different medium in the thesis, it offers practical experience in using frequency-dispersion phenomenon. The main achievements of the thesis are as follows:
1. Physical model experiment studying indoor
Construct wideband (100KHz--2.8GHz) electromagnetic wave signal analyzing system base on NI company's key hardware and software of high frequency signal transmitting and receiving. Simulate high resistance medium by forty-three concrete modules (100cmxl0cmx50cm) continuously arranged and low resistance medium by three cast iron modules (same scale). Transmit and receive electromagnetic wave at the height of 55cm over the model. Measure each module reflective intensity of 0.5GHz, 1.0GHz, 1.5GHz electromagnetic wave in the condition of non-overcast and overcast water layer of 15 cm thickness. By analyzing and computing observe data, the main conclusion of the experiment indoor are as follows:
(1) On non-overcast water layer, for concrete modules, reflective intensity of frequency 1.0GHz is less 51.98% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 1.0396/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 41.97% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.8394/GHz between 1.5GHz and 1.0GHz . Concrete modules' frequency-dispersion of reflective amplitude variety non-linear . For cast iron modules, reflective intensity of frequency 1.0GHz is less 43.73% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 0.8746/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 38.55% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.7710/GHz between 1.5GHz and 1.0GHz . Cast iron modules' frequency-dispersion of reflective amplitude variety non-linear, too. Low resistance cast iron modules' the value of frequency-dispersion is less than high resistance concrete modules' in the same frequency difference. The attenuation of reflective intensity become weaker in the high frequency band than in low frequency band.
(2) On overcast water layer, for concrete modules, reflective intensity of frequency 1.0GHz is less 59.92% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 1.1984/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 38.91% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.7782/GHz between 1.5GHz and 1.0GHz . For cast iron modules, reflective intensity of frequency 1.0GHz is less 48.79% than reflective intensity of frequency 0.5GHz, and reflective amplitude frequency-dispersion rate is 0.9758/GHz between 1.0GHz and 0.5GHz ; reflective intensity of frequency 1.5GHz is less 31.79% than reflective intensity of frequency 1.0GHz, and reflective amplitude frequency-dispersion rate is 0.6358/GHz between 1.5GHz and 1.0GHz . Because of the overcast water layer, the value of frequency-dispersion in the low frequency band become stronger, however, the value of frequency-dispersion in the high frequency band become weaker.
2. Physical model experiment studying local
Measure the different frequency of 0.1 GHz, 0.4 GHz, 0.9 GHz reflective intensity of the cast iron pipe embodied in soil of 100 cm depth by TerraSIRch SIR-3000 Ground Probe Radar system.
By analyzing and computing observe data, for cast iron pipe, reflective intensity of frequency 0.4GHz is less 0.1423% than reflective intensity of frequency 0.1GHz, and reflective amplitude frequency-dispersion rate is 0.004745/GHz between 0.4GHz and 0.1GHz ; reflective intensity of frequency 0.9GHz is less 0.4487% than reflective intensity of frequency 0.4GHz, and reflective amplitude frequency-dispersion rate is 0.008974/GHz between 0.9GHz and 0.4GHz . Cast iron pipe frequency-dispersion of reflective amplitude variety non-linear, and The attenuation of reflective intensity become stronger in the high frequency band than in low frequency band.
引文
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