本文選題：非飽和黃土 + 三軸試驗　； 參考：《西安理工大學(xué)》2017年碩士論文

【摘要】：黃土是具有水敏性的特殊土,天然狀態(tài)的黃土大多處于非飽和狀態(tài)。在黃土地區(qū)的實際工程中,不同的開挖及回填方式會讓土體經(jīng)歷不同的應(yīng)力路徑,進一步影響土體的變形強度及屈服特性。氣體滲透系數(shù)是非飽和土固結(jié)分析的參數(shù)之一,氣體滲透系數(shù)受干密度、含水率的影響。應(yīng)力狀態(tài)也對土體滲氣特性產(chǎn)生影響。研究黃土在不同應(yīng)力路徑下變形、強度、屈服及滲氣特性具有重要的理論及實際意義。論文首先對原狀黃土進行了控制吸力的等向壓縮、常規(guī)三軸壓縮以及等應(yīng)力比壓縮試驗�；诘认驂嚎s試驗,分析了變形及屈服特性,研究了吸力對變形特性指標的影響,彈性指數(shù)隨吸力的變化基本不變,壓縮指數(shù)隨吸力的增大而增大;屈服應(yīng)力隨吸力的增大而增大�；诔Ｒ�(guī)三軸壓縮試驗,分析了吸力對變形強度及屈服特性,應(yīng)力應(yīng)變關(guān)系呈硬化型,非飽和黃土強度符合Fredlund強度準則。基于等應(yīng)力比壓縮試驗,分析了吸力、應(yīng)力比對變形及屈服特性指標的影響,研究表明,同一吸力狀態(tài)下,相同軸向變形時,偏應(yīng)力隨應(yīng)力比的增大而增大,相同吸力時,彈性指數(shù)隨應(yīng)力比的變化基本不變,壓縮指數(shù)隨應(yīng)力比的增大而增大。相同應(yīng)力比時,彈性指數(shù)、壓縮指數(shù)皆隨吸力的增大而增大�；谌N應(yīng)力路徑下的試驗結(jié)果,得到在q-p平面內(nèi)的屈服線并非對稱于p軸,而是對稱于k0線,并提出屈服線的數(shù)學(xué)表達式。其次,進行了等向壓縮及三軸壓縮應(yīng)力條件下的滲氣試驗。研究了含水率、飽和度、凈平均應(yīng)力、固結(jié)圍壓、剪應(yīng)力水平以及應(yīng)力產(chǎn)生的孔隙比等因素對滲氣系數(shù)的影響,結(jié)果表明:相同含水率時,滲氣系數(shù)隨凈平均應(yīng)力與固結(jié)應(yīng)力以及剪應(yīng)力水平的增大而減小;相同凈平均應(yīng)力時,滲氣系數(shù)隨含水率與飽和度的增大而減小;相同含水率時,滲氣系數(shù)隨應(yīng)力引起孔隙比的增大而減小;且同一含水率,不同固結(jié)圍壓、剪應(yīng)力水平下的ka~e關(guān)系點分布在一帶狀區(qū)域內(nèi),可以歸一。不同含水率、固結(jié)圍壓、剪應(yīng)力水平下滲氣系數(shù)與修正氣體飽和度可以歸一并建立起數(shù)學(xué)表達式。
[Abstract]:Loess is a special soil with water sensitivity, and the natural loess is mostly in unsaturated state. In the actual engineering of loess area, different excavation and backfill methods will make the soil go through different stress paths, which will further affect the deformation strength and yield characteristics of the soil. The gas permeability coefficient is one of the parameters in the consolidation analysis of unsaturated soil. The gas permeability coefficient is affected by dry density and moisture content. The stress state also affects the gas permeability of soil. It is of great theoretical and practical significance to study the deformation, strength, yield and gas permeability of loess under different stress paths. In this paper, the isotropic compression, conventional triaxial compression and iso-stress ratio compression tests of undisturbed loess are carried out. Based on the isotropic compression test, the deformation and yield characteristics are analyzed, and the influence of suction on the deformation characteristics is studied. The elastic index is basically unchanged with the suction, and the compression index increases with the increase of the suction. The yield stress increases with the increase of suction. Based on the conventional triaxial compression tests, the deformation strength and yield characteristics of suction are analyzed. The stress-strain relationship is of hardening type, and the strength of unsaturated loess conforms to the Fredlund strength criterion. Based on the compression test of equal stress ratio, the effects of suction, stress ratio on deformation and yield characteristics are analyzed. The results show that under the same suction state and the same axial deformation, the deflection stress increases with the increase of stress ratio, and with the same suction, the deflection stress increases with the increase of stress ratio. The elastic exponent is almost unchanged with the stress ratio, and the compression index increases with the increase of the stress ratio. At the same stress ratio, the elastic exponent and compression exponent increase with the increase of suction. Based on the experimental results under three stress paths, it is obtained that the yield line in the q-p plane is not symmetric to the p axis, but to the k _ 0 line, and the mathematical expression of the yield line is presented. Secondly, the gas permeation tests were carried out under isotropic compression and triaxial compression stress. The effects of water content, saturation, net mean stress, consolidation confining pressure, shear stress level and void ratio produced by stress on permeability coefficient are studied. The permeability coefficient decreases with the increase of net average stress, consolidation stress and shear stress level; at the same net average stress, the permeability coefficient decreases with the increase of water content and saturation; at the same water content, the permeability coefficient decreases with the increase of water content and saturation. The permeability coefficient decreases with the increase of void ratio caused by stress, and the ka~e relation points of the same water content, different consolidation confining pressure and shear stress level are distributed in a zonal region, which can be reunified. The mathematical expressions of permeability coefficient and modified gas saturation under different water content, consolidation confining pressure, shear stress level and modified gas saturation can be established.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU444

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