填方区非饱和黄土体水分迁移及变形规律研究

发布时间：2018-07-26 10:39

【摘要】：黄土填方工程施工引起的地下水位变化、管道破裂等问题使黄土体长期处于增湿-减湿循环条件下,水分迁移不断浸润地基,改变其湿度状态,导致土体工程性质劣化,产生不均匀沉降,建筑物变形破坏,造成大量工程经济损失。以延安填方区非饱和黄土土体为研究对象,通过水分迁移试验,分析了黄土体水分迁移规律;通过基质吸力测定试验,得到了黄土土-水特征曲线,并在此基础上建立了水分迁移后单位体积土体含水率变化方程,探讨非饱和黄土水分迁移机理;结合增湿试验,分析了压实黄土增湿变形特性;最后,通过ABAQUS软件建立了水分迁移模型和填方区增湿变形模型,进行了非饱和黄土水分迁移及增湿变形模拟,探明了干密度、含水率和增湿减湿循环对水分迁移及增湿变形的影响规律。主要结论如下:(1)采用自制水分迁移系统开展非饱和黄土水分迁移试验,发现水分迁移速率随增湿减湿循环次数增加、干密度增大、初始含水率减小而减慢。水分迁移稳定后,终态体积含水率随迁移高度的增大而小幅度减小,干密度及初始含水率越小,终态体积含水率越大。(2)通过对土体减湿过程和两次减湿-增湿循环过程的基质吸力进行测定,发现干密度越大的土样基质吸力越大,且高含水率时,干密度对基质吸力影响较小,低含水率时影响较大。干湿循环条件下,土-水特征曲线形成明显的滞回圈,且干湿循环对基质吸力的影响是逐渐减弱的。(3)根据水分迁移试验结果,结合黄土土-水特征曲线建立了水分迁移稳定后单位体积土体含水率变化方程,可用于预测填方体终态体积含水率。(4)压实黄土增湿变形系数随初始含水率和干密度的减小、干湿循环次数的增加而增大。高压下黄土湿陷敏感性较强,干湿循环对土体增湿变形特性的影响是逐渐减弱的,提高干密度可有效控制压实黄土增湿变形。
[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.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444;TU433

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