考虑时间效应的黄土变形特性及工程应用研究
发布时间：2018-11-14 07:31
【摘要】：随着我国西部大开发建设的加快,黄土变形的相关特性对工程具有重要意义。目前针对黄土变形的时间效应研究较少。基于此,本文以西安黄土为研究对象,着重研究分析了在偏应力作用下黄土变形的时间效应特性。通过对重塑黄土进行三轴试验,研究了不同的围压、含水率、干密度对黄土变形随时间变化的相关特性。结果表明:在偏应力作用下,黄土的轴向应变-时间曲线表现为三个阶段:线性变形阶段,非稳定变形阶段和稳定变形阶段。在围压较低,偏应力较大的情况下,黄土变形达到稳定阶段所需的时间较长;在围压较低、偏应力较小的情况下,黄土变形达到稳定阶段所需的时间较短。而在高围压下,无论偏应力是大是小,黄土变形在很短的时间内就达到稳定。当含水率较高时,黄土在不同偏应力作用下,一定时间内的轴向应变量比含水率较低时轴向应变量大。不同干密度的黄土,在偏应力较低时,其轴向应变处于稳定变形阶段的时间较长,随着偏应力的增加,其轴向应变处于非稳定变形阶段的时间较长。分析黄土的应力应变时间效应关系曲线可以得出:黄土的应力应变时间效应曲线有明显的非线性特征,随着时间的增加,曲线族越来越靠近应变轴。不同围压、含水率、干密度下黄土的应力应变时间效应曲线,在不同的时间节点存在一定差异。参考黄土蠕变特性的Singh-Mitchell模型和Mesri模型以及双曲线模型对试验数据进行拟合,结果表明该地区重塑黄土试样采用双曲线模型拟合时,能够较好的模拟黄土变形规律,且该模型具有参数易取,拟合程度较好等优点。运用GeoStudio分析软件,采用试验拟合的双曲线模型建立土体变形模量随时间变化的函数表达式,分析基坑边坡黄土在不同偏应力作用下竖向应变大小随时间变化情况及应力应变的时间效应曲线特征,并将计算结果与试验数据进行对比。结果表明:在不同偏应力作用下,基坑边坡黄土竖向应变大小具有明显的时间效应,计算软件采用双曲线模型能够较好的拟合试验数据,验证了该模型的准确性与合理性。
[Abstract]:With the rapid development of western China, the characteristics of loess deformation are of great significance to the project. At present, there are few researches on the time effect of loess deformation. Based on this, this paper takes Xi'an loess as the research object, emphatically studies and analyzes the time effect characteristic of loess deformation under the action of partial stress. Through triaxial tests on remolded loess, the correlation characteristics of different confining pressure, moisture content and dry density on loess deformation with time were studied. The results show that the axial strain-time curves of loess show three stages: linear deformation, unstable deformation and stable deformation. Under the condition of lower confining pressure and larger deflection stress, the time required for loess deformation to reach stable stage is longer, and the time for loess deformation to reach stable stage is shorter when confining pressure is lower and deflection stress is small. However, under high confining pressure, the deformation of loess is stable in a very short time, no matter whether the deflection stress is large or small. When the moisture content is high, the axial strain of loess is larger than that of low moisture content in a certain time under the action of different stress. For loess with different dry densities, the axial strain is in the stable deformation stage for a long time when the deflection stress is low, and the axial strain is in the unstable deformation stage with the increase of the deflection stress. By analyzing the stress-strain time effect curve of loess, it can be concluded that the stress-strain time effect curve of loess has obvious nonlinear characteristics, and with the increase of time, the family of curves is closer to the strain axis. The stress-strain time effect curves of loess under different confining pressure, moisture content and dry density are different in different time nodes. Singh-Mitchell model, Mesri model and hyperbolic model are used to fit the test data. The results show that the deformation law of loess can be well simulated when the remolded loess specimen is fitted by hyperbolic model. The model has the advantages of easy to get parameters and good fitting degree. Using GeoStudio analysis software, the hyperbolic model of test fitting is used to establish the functional expression of the variation of soil deformation modulus with time. The variation of vertical strain with time and the characteristic of time-effect curve of stress-strain in loess slope of foundation pit under different deflection stress are analyzed, and the calculated results are compared with experimental data. The results show that the vertical strain of loess in excavation slope has obvious time effect under the action of different deflection stress. The hyperbolic model can fit the test data well and verify the accuracy and rationality of the model.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444
，
本文编号：2330482
[Abstract]:With the rapid development of western China, the characteristics of loess deformation are of great significance to the project. At present, there are few researches on the time effect of loess deformation. Based on this, this paper takes Xi'an loess as the research object, emphatically studies and analyzes the time effect characteristic of loess deformation under the action of partial stress. Through triaxial tests on remolded loess, the correlation characteristics of different confining pressure, moisture content and dry density on loess deformation with time were studied. The results show that the axial strain-time curves of loess show three stages: linear deformation, unstable deformation and stable deformation. Under the condition of lower confining pressure and larger deflection stress, the time required for loess deformation to reach stable stage is longer, and the time for loess deformation to reach stable stage is shorter when confining pressure is lower and deflection stress is small. However, under high confining pressure, the deformation of loess is stable in a very short time, no matter whether the deflection stress is large or small. When the moisture content is high, the axial strain of loess is larger than that of low moisture content in a certain time under the action of different stress. For loess with different dry densities, the axial strain is in the stable deformation stage for a long time when the deflection stress is low, and the axial strain is in the unstable deformation stage with the increase of the deflection stress. By analyzing the stress-strain time effect curve of loess, it can be concluded that the stress-strain time effect curve of loess has obvious nonlinear characteristics, and with the increase of time, the family of curves is closer to the strain axis. The stress-strain time effect curves of loess under different confining pressure, moisture content and dry density are different in different time nodes. Singh-Mitchell model, Mesri model and hyperbolic model are used to fit the test data. The results show that the deformation law of loess can be well simulated when the remolded loess specimen is fitted by hyperbolic model. The model has the advantages of easy to get parameters and good fitting degree. Using GeoStudio analysis software, the hyperbolic model of test fitting is used to establish the functional expression of the variation of soil deformation modulus with time. The variation of vertical strain with time and the characteristic of time-effect curve of stress-strain in loess slope of foundation pit under different deflection stress are analyzed, and the calculated results are compared with experimental data. The results show that the vertical strain of loess in excavation slope has obvious time effect under the action of different deflection stress. The hyperbolic model can fit the test data well and verify the accuracy and rationality of the model.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444
，
本文编号：2330482
本文链接：https://www.wllwen.com/jianzhugongchenglunwen/2330482.html
