【摘要】：黃土填方工程施工引起的地下水位變化、管道破裂等問題使黃土體長期處于增濕-減濕循環(huán)條件下,水分遷移不斷浸潤地基,改變其濕度狀態(tài),導(dǎo)致土體工程性質(zhì)劣化,產(chǎn)生不均勻沉降,建筑物變形破壞,造成大量工程經(jīng)濟(jì)損失。以延安填方區(qū)非飽和黃土土體為研究對象,通過水分遷移試驗,分析了黃土體水分遷移規(guī)律;通過基質(zhì)吸力測定試驗,得到了黃土土-水特征曲線,并在此基礎(chǔ)上建立了水分遷移后單位體積土體含水率變化方程,探討非飽和黃土水分遷移機(jī)理;結(jié)合增濕試驗,分析了壓實黃土增濕變形特性;最后,通過ABAQUS軟件建立了水分遷移模型和填方區(qū)增濕變形模型,進(jìn)行了非飽和黃土水分遷移及增濕變形模擬,探明了干密度、含水率和增濕減濕循環(huán)對水分遷移及增濕變形的影響規(guī)律。主要結(jié)論如下:(1)采用自制水分遷移系統(tǒng)開展非飽和黃土水分遷移試驗,發(fā)現(xiàn)水分遷移速率隨增濕減濕循環(huán)次數(shù)增加、干密度增大、初始含水率減小而減慢。水分遷移穩(wěn)定后,終態(tài)體積含水率隨遷移高度的增大而小幅度減小,干密度及初始含水率越小,終態(tài)體積含水率越大。(2)通過對土體減濕過程和兩次減濕-增濕循環(huán)過程的基質(zhì)吸力進(jìn)行測定,發(fā)現(xiàn)干密度越大的土樣基質(zhì)吸力越大,且高含水率時,干密度對基質(zhì)吸力影響較小,低含水率時影響較大。干濕循環(huán)條件下,土-水特征曲線形成明顯的滯回圈,且干濕循環(huán)對基質(zhì)吸力的影響是逐漸減弱的。(3)根據(jù)水分遷移試驗結(jié)果,結(jié)合黃土土-水特征曲線建立了水分遷移穩(wěn)定后單位體積土體含水率變化方程,可用于預(yù)測填方體終態(tài)體積含水率。(4)壓實黃土增濕變形系數(shù)隨初始含水率和干密度的減小、干濕循環(huán)次數(shù)的增加而增大。高壓下黃土濕陷敏感性較強(qiáng),干濕循環(huán)對土體增濕變形特性的影響是逐漸減弱的,提高干密度可有效控制壓實黃土增濕變形。
[Abstract]:The change of groundwater level caused by the construction of loess fill project and the rupture of pipeline make the loess body under the condition of humidification and desiccant cycle for a long time, and the water migration continuously infiltrates the foundation, changes its humidity state, and results in the deterioration of the engineering properties of soil. Uneven settlement, building deformation and destruction, resulting in a large number of engineering economic losses. Taking unsaturated loess soil in Yan'an fill area as the research object, the water migration law of loess body is analyzed by water migration test, and the characteristic curve of loess soil-water is obtained by matrix suction test. On this basis, the change equation of soil moisture content per unit volume after water transfer is established, and the moisture migration mechanism of unsaturated loess is discussed, and the humidification deformation characteristics of compacted loess are analyzed in combination with humidification test. The moisture migration model and the moisture increasing deformation model in the filling area were established by ABAQUS software. The moisture migration and humidification deformation of unsaturated loess were simulated, and the dry density was proved. The effect of moisture content and humidification cycle on moisture migration and humidification deformation. The main conclusions are as follows: (1) the experiment of unsaturated loess water migration with self-made water migration system shows that the water migration rate increases with the increase of moisture and moisture reduction cycles, the dry density increases, and the initial moisture content decreases. After steady water migration, the final volume water content decreases with the increase of migration height, and the dry density and initial moisture content decrease. The larger the final volume moisture content is. (2) through the measurement of the matrix suction of the soil during the dehumidification process and the two dehumidification and humidification cycles, it is found that the larger the dry density of the soil is, the greater the suction of the matrix is, and when the moisture content is high, The dry density had little effect on the suction of the substrate, but had a great effect on the low moisture content. Under dry and wet cycle conditions, the characteristic curve of soil-water formed an obvious hysteresis loop, and the effect of dry-wet cycle on the matrix suction was gradually weakened. (3) according to the results of water migration test, Based on the characteristic curve of loess soil-water, the variation equation of soil moisture content per unit volume after water migration is established, which can be used to predict the final volume water content of fill body. (4) the deformation coefficient of compacted loess decreases with the initial moisture content and dry density. The number of dry and wet cycles increased. The sensitivity of loess collapsing under high pressure is strong, the effect of dry and wet cycle on soil humidification deformation is gradually weakened, and increasing dry density can effectively control the humidification deformation of compacted loess.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU444;TU433

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