在TDR 壓力鍋實驗與變化的土壤乾濕速率和環境因素分析土壤的介電譜;Dielectric spectrum analysis of soils due to drying-wetting rate and environment influences using TDR pressure plate

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题名:	在TDR 壓力鍋實驗與變化的土壤乾濕速率和環境因素分析土壤的介電譜;Dielectric spectrum analysis of soils due to drying-wetting rate and environment influences using TDR pressure plate
作者:	艾札;Azhar, Muhammad
贡献者:	土木工程學系
关键词:	土壤介電頻譜;時域反射法;乾濕速率;向量網絡分析儀;Soil dielectric spectrum;time domain reflectometry;drying-wetting rate;vector network analyzer
日期:	2022-09-30
上传时间:	2022-10-04 10:51:29 (UTC+8)
出版者:	國立中央大學
摘要:	淺層滑坡是坡地災害之一，此類滑坡一般發生在岩盤上覆有殘餘土的斜坡，往往是由於降雨入滲，改變了非飽和土的含水量，使基質吸力降低，影響土壤的穩定性。因此，監測邊坡非飽和土層的含水量和特性是必要的。雖然通過地電阻 (ERT) 作為土壤含水量與電阻率剖面轉換，但電阻率與含水量關係受地質和水文因素的影響。因此，時域反射儀（Time Domain Reflectometry, TDR）常被用來測量土壤水分含量和導電率（electrical conductivity, EC）/電阻率，此外，乾濕速率控制著土壤水分特性與EC的關係，需要從鹽度（電導率）和pH值等環境因素進一步考察。因此，本研究以TDR壓力鍋裝置檢測低潤濕和乾燥速率下土壤的介電頻譜。本試驗採用國立中央大學不同乾密度的紅黏土（如1.35 g/〖cm〗^3 和1.45 g/〖cm〗^3），並研究各種水質鹽度（100~700 μS/cm）和pH值（5~7）的影響。同時，本研究初步採用向量網路分析儀（Vector Network Analyzer, VNA）（1 MHz至1 GHz頻率範圍）用於比對TDR的介電頻譜波形結果。試驗結果顯示，採用TDR波形全反算分析和頻率域相速速度法，對土壤的介電頻譜分析結果非常吻合，特別是在0.1 GHz~1 GHz頻率範圍內。結果顯示乾燥速率較高的土壤的介電頻譜在每個週期之間的差異大於乾燥速率較低的土壤。然而，觀察TDR和VNA的介電頻譜，介電常數之間的差距在高頻上更大。VNA需要更充分的測試與計算才能產生更加合理的結果。;Shallow landslide is one of the natural disasters that arise on slope land. This kind of landslide, which generally occurs on slopes with residual soils overlying bedrock, is often caused by infiltration of rainfall, changing the water content of the unsaturated soil. Then, the decreasing matric suction reduces the stability of the soil. Hence, monitoring the water content and characteristic of the unsaturated soil layer on the slope is necessary. Although the soil water content is correlated with electrical resistivity through Electrical Resistivity Tomography (ERT), resistivity is influenced by geological and hydrological factors. Therefore, Time Domain Reflectometry (TDR) is utilized to measure the soil moisture content and electrical conductivity (EC)/resistivity to address the problem. Moreover, the drying-wetting rate controls the relationship between soil water characteristics and EC, and it needs further examination from environmental factors, such as salinity (conductivity) and pH value. Accordingly, this study involves TDR to retrieve the dielectric spectrum of soil from the TDR Pressure Plate device with a low wetting and drying rate. The soil red clay soil of National Central University with different dry density such as 1.35 g/cm3 and 1.45 g/cm3 was employed to investigate the effect of various salinity (100-700 μS/cm) and pH values (5-7). Meanwhile, the Vector Network Analyzer (VNA) (1 MHz to 1 GHz frequency range) was operated to verify the dielectric spectrum results from the TDR waveform. The result of dielectric spectrum analysis of soil from full inversion analysis and phase velocity method fit greatly, especially at the 0.1 GHz to 1 GHz frequency range. The result indicates that the dielectric spectrum of soil with a higher drying rate will have a higher difference between each cycle than soil with a lower drying rate. However, the gaps in the dielectric spectrum between TDR and VNA are higher on the high frequency. More adequate tests and calculation procedures are needed in the VNA test to produce more reasonable results.
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