| 摘要: | 台灣位於環太平洋地震帶上，主要由菲律賓海板塊和歐亞板塊的碰撞而產生的島嶼，其屬於較年輕的地質，所以地質處於較不穩定且較破碎之狀態。而臺灣屬於亞熱帶季風氣候，主要的降雨來自梅雨與颱風。然而，每當豪雨發生時，山區時常發生土石鬆動與崩滑之現象，大量的土石崩落已影響到民眾的生命財產與安全。由於研究指出影響淺層滑坡產生的滑動的關鍵因素在於降雨入滲，而監測大範圍土壤體積含水量剖面於大面積邊坡穩定分析是相當有用的。
本研究使用時域反射法(Time Domain Reflectometry, TDR)之設備與地電阻影像剖面法(Electrical Resistivity Tomography, ERT)。藉由電阻率(與導電度為倒數關係)與體積含水量的關係，來繪製出大範圍體積含水量剖面圖。並且搭配吸力計來量測基質吸力，藉由土壤水分特徵曲線(Soil Moisture Characteristic Curve, SWCC)來繪製出大範圍吸力剖面圖。
由於前期研究指出含水量與導電度存在非唯一關係，且乾溼速率是影響遲滯效應的關鍵因素，所以本研究擬定找出其他產生遲滯效應的因素，以評估能順利繪製體積含水量剖面圖。本研究藉由砂箱實驗來找出何種因素對於遲滯效應影響最大，如緊實與鬆散的紅土、酸雨與中性的雨水，與不同的水質導電度。且由上述的每個因素再搭配急降雨，來比對何種因素會加劇遲滯效應影響，又或者影響程度相當。成果顯示較高的水質導電度並無法產生遲滯效應，較高的密度與酸雨能看到類似遲滯迴圈的現象。最後藉由實驗中擷取到的反射訊號進行頻譜分析，作為初步可行性評估。以及在感測範圍內，試體含水量較於平均時，PVA(Phase velocity analysis)頻譜與TDR全波形反算分析法(Full waveform inversion analysis)頻譜具有非常不錯的相似程度，以及PVA在分析速度與程式輕量化上明顯優於TDR全波形反算分析法(Full waveform inversion analysis)。
;Taiwan is featured with the frequent earthquakes by Philippine Sea Plate and Eurasian Plate which collide together. Also, Taiwan is subtropical monsoon climate, and the rainfall is primary for the rainy season and typhoon. However, whenever torrential rains occur, the mountainous areas often loosen and collapsed. The landslides have affected people′s lives, property and safety. Since the study pointed out that the key factor affecting the sliding caused by shallow landslides is rainfall infiltration, the monitoring of a large-scale soil volumetric water content profile is quite useful for the slope stability analysis.
In the study, we use Time Domain Reflectometry (TDR) and Electrical Resistivity Tomography (ERT) to draw a large-scale soil volumetric water content profile by the relationship between the volumetric water content and electrical conductivity (EC), which is reciprocal for electrical resistivity. And also use a tensiometer to draw a large-scale soil matric suction profile by the relationship for Soil-Water characteristic curve. The relationship between the volumetric water content and electrical conductivity has a non-unique relationship (Hysteresis). The previous research points out that the drying-wetting rate is the key factor affecting the hysteresis effect, so finding out other factors that produce the hysteresis effect is an important key to draw the volumetric water content profile.
In the study, we wanted to find out which factors have the influence on the hysteresis through the sandbox test, such as dense and loose sand, acid factors with the torrential rainfall. The results show that higher water EC does not produce hysteresis, and density and acid rainfall water can see a phenomenon of hysteresis. Finally, TDR spectrum analysis is carried out in the experiment as a preliminary feasibility assessment. When the water content of the specimen is uniformly distributed, the PVA (Phase velocity analysis) spectrum and the TDR full waveform inversion analysis spectrum have a very good degree of similarity. Furthermore, PVA has advantages of program lightweight and higher speed for analysis. |
