【摘要】：非飽和土與飽和土的根本差異在于非飽和土中的孔隙水壓力為負值�？紫稓鈮号c負孔隙水壓力的差值定義為基質(zhì)吸力,用來體現(xiàn)非飽和土的應力特征。將基質(zhì)吸力與土含水率的關系曲線稱為土-水特征曲線(Soil-Water Characteristic Curve),簡稱SWCC。SWCC是非飽和土的一個重要本構(gòu)關系,可以用來分析和預測土的變形、強度和滲透性,因此SWCC是非飽和土研究的基礎�；|(zhì)吸力測試方法較多,其中濾紙法最為快捷、簡便且量程大。本文取陜西涇陽L1和L5黃土樣,在ASTM D5298-10的基礎上,研究濾紙法測試基質(zhì)吸力的操作過程,重點對土樣的制備和試驗條件、濾紙的稱量、平衡時間等關鍵步驟進行分析和改進,將測試結(jié)果與其他方法進行對比,主要結(jié)論有:1)實驗密封條件采用錫紙包裹并蠟封的方法代替ASTM D5298-10推薦的密封罐,解決了密封罐易造成密封不嚴及取放土樣不便的問題,密封結(jié)果更為理想;2)由鋁盒或者保鮮袋為濾紙的容器稱量濾紙改為直接將濾紙放在天平托盤上稱量,提高了稱量濾紙的精度;3)對于同一種土,多組環(huán)刀聯(lián)合測試與只采用一組環(huán)刀測試相比,更易于操作,且減小了操作過程中的誤差;4)土樣與濾紙的水勢平衡時間與土樣的干密度關系小,與土樣的含水率關系較大,含水率越大平衡時間越短,反之,平衡時間越長,對于涇陽L1和L5黃土,土樣含水率小于5%時,建議平衡時間13天以上;土樣含水率介于5%~20%之間,建議平衡時間為10天以上;含水率大于20%時,建議平衡時間為5天以上;5)分別采用Gardner模型、Van Genuchten模型和FredlundXing模型對濾紙法所獲基質(zhì)吸力及土樣實際含水率進行SWCC擬合,FredlundXing模型擬合度最高;6)通過將已有采用張力計、壓力板儀、壓力膜儀、滲析法及濾紙法等測得的黃土SWCC與本文濾紙法測試結(jié)果對比,證明本文推薦的方法和所測試的結(jié)果可靠性高且在全基質(zhì)吸力范圍內(nèi)均較為適用。
[Abstract]:The fundamental difference between unsaturated soil and saturated soil is that the pore water pressure in unsaturated soil is negative. The difference between pore pressure and negative pore water pressure is defined as matrix suction, which is used to reflect the stress characteristics of unsaturated soil. The relation curve between matrix suction and soil moisture content is called the soil-water characteristic curve (Soil-Water Characteristic Curve), which is an important constitutive relation of unsaturated soil. It can be used to analyze and predict the deformation, strength and permeability of soil. Therefore, SWCC is the basis of unsaturated soil research. There are many methods of matrix suction measurement, among which filter paper method is the most rapid, simple and has a large measuring range. On the basis of ASTM D5298-10, the operating process of filter paper method for measuring the suction of the matrix was studied, and the preparation and test conditions of the soil samples, the weighing of filter paper, were studied in this paper, taking the loess samples of Jingyang, Shaanxi Province, as well as the L _ 5 loess samples, and based on ASTM D5298-10. The key steps, such as balance time, are analyzed and improved, and the test results are compared with other methods. The main conclusions are as follows: 1) the experimental sealing conditions are replaced by the seal tank recommended by ASTM D5298-10. The problem that the sealing tank is easy to be sealed and the soil sample is not easy to be taken is solved, and the sealing result is more ideal. 2) the weighing filter paper is changed from the container weighing filter paper of aluminum box or fresh-keeping bag to the weighing paper directly on the balance tray, which improves the accuracy of weighing filter paper; 3) for the same soil, it is easier to operate and the error in the operation process is reduced compared with that of using only one group of ring knives. 4) the water potential equilibrium time of soil sample and filter paper has little relationship with dry density of soil sample, and has a greater relation with soil sample moisture content. The larger the water content is, the shorter the equilibrium time is, otherwise, the longer the equilibrium time is, the longer the balance time is, and the longer the balance time is, the longer the balance time is for Jingyang L1 and L5 loess. When the moisture content of soil sample is less than 5, it is suggested that the balance time be more than 13 days. The water content of soil sample is between 5% and 20%, and the suggested equilibrium time is more than 10 days, and when the moisture content is more than 20, the suggested equilibrium time is more than 5 days. 5) Gardner model, Van Genuchten model and FredlundXing model were used to fit the matrix suction and soil sample moisture content obtained by filter paper method respectively. FredlundXing model had the highest fitting degree. 6) the SWCC of loess measured by tension meter, pressure plate instrument, pressure film meter, dialysis method and filter paper method are compared with the results of filter paper method in this paper. It is proved that the proposed method and the measured results are reliable and applicable in the whole matrix suction range.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU444

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