非饱和重塑黄土的变形、屈服与强度特性的真三轴试验研究

发布时间：2018-04-13 18:54

本文选题：非饱和重塑黄土 + 真三轴试验　；参考：《西安理工大学》2017年硕士论文

【摘要】：黄土地区有越来越多的填土工程,它采用重塑黄土填筑,且呈非饱和状态。因此,开展非饱和重塑黄土强度变形特性的真三轴试验研究,对于分析复杂应力条件下黄土工程遭受入渗增湿和加载作用的变形与强度稳定性具有重要的理论意义。本文采用非饱和土基质吸力控制轴平移技术和真三轴试验,研究了不同基质吸力重塑黄土在中主应力比值和平均球应力保持不变剪切过程的应力应变变化规律,剪切屈服强度变化规律,以及剪切破坏强度变化规律,得到了以下成果:1)采用环刀压样法制备了不同含水率非饱和重塑黄土试样,通过非饱和土固结仪分别控制试样孔隙气压力和孔隙水压力,测试不同基质吸力作用下水分保持稳定状态的非饱和土试样含水率,得到了土水特征曲线。2)利用压样法制备不同含水率的真三轴试样,依据土水特征曲线由试样含水率确定基质吸力,应用轴平移技术控制试样的基质吸力50kPa、80kPa、120kPa、200kPa,在净围压300kPa、400kPa、500kPa、600kPa分别固结,然后控制不同中主应力比值0.0、0.15、0.5、0.7、0.9、1.0,进行了基质吸力和净平均应力保持不变的真三轴剪切试验,得到了相应的试验结果。3)依据剪切过程体应变和有效应力比之间的关系曲线,分析了初始剪切段体应变近似线性变化、产生屈服后的非线性变化到体应变明显增长的发展过程,确定了剪缩屈服有效应力比。分析了不同中主应力比值子午平面上剪切屈服状态的广义剪应力和平均有效应力之间的关系,它们近似呈线性变化,且通过原点。4)分析了一定基质吸力和平均球应力条件下不同中主应力比值剪切过程非饱和土的有效大、小即中、小主应力比和剪切体应变分别随大主应变、中主应变的变化规律。表明基质吸力50kPa-200kPa、平均净应力300kPa-600kPa范围内,非饱和黄土均呈剪缩变形特征;中主应力比值0.0-0.15的非饱和土具有中主应力方向挤伸的变形特征,中主应力比值0.5-1.0的非饱和土具有中主应力方向压缩的变形特征。5)不同基质吸力和平均球应力条件下,非饱和土的广义剪应力和广义剪应变关系曲线表明,随着中主应力比值的增大,剪切破坏时的抗剪强度逐渐减小。不同子午平面内抗剪强度随平均有效应力呈线性变化规律;不同π平面内有效应力抗剪强度近似符合Matsuoka-Nakai强度准则。
[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.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444

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