本文選題：非飽和重塑黃土 + 真三軸試驗�。� 參考：《西安理工大學》2017年碩士論文

【摘要】：黃土地區(qū)有越來越多的填土工程,它采用重塑黃土填筑,且呈非飽和狀態(tài)。因此,開展非飽和重塑黃土強度變形特性的真三軸試驗研究,對于分析復雜應力條件下黃土工程遭受入滲增濕和加載作用的變形與強度穩(wěn)定性具有重要的理論意義。本文采用非飽和土基質(zhì)吸力控制軸平移技術(shù)和真三軸試驗,研究了不同基質(zhì)吸力重塑黃土在中主應力比值和平均球應力保持不變剪切過程的應力應變變化規(guī)律,剪切屈服強度變化規(guī)律,以及剪切破壞強度變化規(guī)律,得到了以下成果:1)采用環(huán)刀壓樣法制備了不同含水率非飽和重塑黃土試樣,通過非飽和土固結(jié)儀分別控制試樣孔隙氣壓力和孔隙水壓力,測試不同基質(zhì)吸力作用下水分保持穩(wěn)定狀態(tài)的非飽和土試樣含水率,得到了土水特征曲線。2)利用壓樣法制備不同含水率的真三軸試樣,依據(jù)土水特征曲線由試樣含水率確定基質(zhì)吸力,應用軸平移技術(shù)控制試樣的基質(zhì)吸力50kPa、80kPa、120kPa、200kPa,在凈圍壓300kPa、400kPa、500kPa、600kPa分別固結(jié),然后控制不同中主應力比值0.0、0.15、0.5、0.7、0.9、1.0,進行了基質(zhì)吸力和凈平均應力保持不變的真三軸剪切試驗,得到了相應的試驗結(jié)果。3)依據(jù)剪切過程體應變和有效應力比之間的關(guān)系曲線,分析了初始剪切段體應變近似線性變化、產(chǎn)生屈服后的非線性變化到體應變明顯增長的發(fā)展過程,確定了剪縮屈服有效應力比。分析了不同中主應力比值子午平面上剪切屈服狀態(tài)的廣義剪應力和平均有效應力之間的關(guān)系,它們近似呈線性變化,且通過原點。4)分析了一定基質(zhì)吸力和平均球應力條件下不同中主應力比值剪切過程非飽和土的有效大、小即中、小主應力比和剪切體應變分別隨大主應變、中主應變的變化規(guī)律。表明基質(zhì)吸力50kPa-200kPa、平均凈應力300kPa-600kPa范圍內(nèi),非飽和黃土均呈剪縮變形特征;中主應力比值0.0-0.15的非飽和土具有中主應力方向擠伸的變形特征,中主應力比值0.5-1.0的非飽和土具有中主應力方向壓縮的變形特征。5)不同基質(zhì)吸力和平均球應力條件下,非飽和土的廣義剪應力和廣義剪應變關(guān)系曲線表明,隨著中主應力比值的增大,剪切破壞時的抗剪強度逐漸減小。不同子午平面內(nèi)抗剪強度隨平均有效應力呈線性變化規(guī)律;不同π平面內(nèi)有效應力抗剪強度近似符合Matsuoka-Nakai強度準則。
[Abstract]:There are more and more filling projects in loess area.Therefore, it is of great theoretical significance to study the true triaxial test of the strength and deformation characteristics of unsaturated remolded loess under complex stress conditions for loess engineering subjected to infiltration, humidification and loading.In this paper, the stress and strain changes of the remolded loess with different matrix suction in the process of constant shear stress and average spherical stress are studied by using the technique of matrix suction control axial translation and true triaxial test.The variation law of shear yield strength and shear failure strength are obtained as follows: 1) the unsaturated remolded loess specimens with different moisture content are prepared by the annular knife compression method.The pore gas pressure and pore water pressure of the unsaturated soil were controlled by the unsaturated soil consolidation instrument, and the moisture content of the unsaturated soil in stable state under the action of different matrix suction was measured.The true triaxial samples with different moisture content were prepared by the pressure sample method. The matrix suction was determined by the soil water characteristic curve. The matrix suction of the sample was controlled by axial translation technique. The matrix suction of the sample was controlled by the axial translation technique, and consolidated at the net confining pressure of 300kPa400kPa500kPa500kPa, and the axial translation technique was used to control the matrix suction of the sample at 300kPa400kPa500kPa600kPa, respectively at net confining pressure (300kPa400kPa500kPa600kPa).Then, the true triaxial shear tests with constant matrix suction and net average stress were carried out under the control of 0.00. 15 / 0. 5 / 0. 7 / 0. 9 / 0. 0. 0. The corresponding test results. 3) according to the curves of the relationship between bulk strain and effective stress ratio in shear process,The approximate linear variation of bulk strain in initial shear section is analyzed, and the nonlinear variation after yield to the obvious increase of bulk strain is analyzed, and the effective stress ratio of shear shrinkage yield is determined.The relationship between the generalized shear stress and the average effective stress in the shear yield state on the meridian plane with different mid-principal stress ratios is analyzed.Through origin .4), the effective large, small, small principal stress ratio and shear body strain of unsaturated soils with different medium principal stress ratios under certain matrix suction and mean spherical stress are analyzed, respectively.The variation of the principal strain.The results show that in the range of average net stress (300kPa-600kPa) of 50 kPa-200kPa, unsaturated loess is shear-shrinkage deformation, and unsaturated soil with medium principal stress ratio 0.0-0.15 has the deformation characteristic of extrusion in the direction of medium principal stress.The unsaturated soil with the ratio of 0.5-1.0 has the deformation characteristics of compression in the direction of medium principal stress. 5) under the conditions of different matrix suction and mean spherical stress, the curves of generalized shear stress and generalized shear strain of unsaturated soil show that the relationship between the generalized shear stress and the generalized shear strain of the unsaturated soil can be obtained.With the increase of the ratio of medium principal stress, the shear strength decreases gradually during shear failure.The shear strength of different meridional plane varies linearly with the average effective stress, and the shear strength of the effective stress in different 蟺 plane approximately accords with the Matsuoka-Nakai criterion.
【學位授予單位】：西安理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU444

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