考慮時間效應(yīng)的黃土變形特性及工程應(yīng)用研究
發(fā)布時間：2018-11-14 07:31
【摘要】：隨著我國西部大開發(fā)建設(shè)的加快,黃土變形的相關(guān)特性對工程具有重要意義。目前針對黃土變形的時間效應(yīng)研究較少�；诖�,本文以西安黃土為研究對象,著重研究分析了在偏應(yīng)力作用下黃土變形的時間效應(yīng)特性。通過對重塑黃土進行三軸試驗,研究了不同的圍壓、含水率、干密度對黃土變形隨時間變化的相關(guān)特性。結(jié)果表明:在偏應(yīng)力作用下,黃土的軸向應(yīng)變-時間曲線表現(xiàn)為三個階段:線性變形階段,非穩(wěn)定變形階段和穩(wěn)定變形階段。在圍壓較低,偏應(yīng)力較大的情況下,黃土變形達到穩(wěn)定階段所需的時間較長;在圍壓較低、偏應(yīng)力較小的情況下,黃土變形達到穩(wěn)定階段所需的時間較短。而在高圍壓下,無論偏應(yīng)力是大是小,黃土變形在很短的時間內(nèi)就達到穩(wěn)定。當(dāng)含水率較高時,黃土在不同偏應(yīng)力作用下,一定時間內(nèi)的軸向應(yīng)變量比含水率較低時軸向應(yīng)變量大。不同干密度的黃土,在偏應(yīng)力較低時,其軸向應(yīng)變處于穩(wěn)定變形階段的時間較長,隨著偏應(yīng)力的增加,其軸向應(yīng)變處于非穩(wěn)定變形階段的時間較長。分析黃土的應(yīng)力應(yīng)變時間效應(yīng)關(guān)系曲線可以得出:黃土的應(yīng)力應(yīng)變時間效應(yīng)曲線有明顯的非線性特征,隨著時間的增加,曲線族越來越靠近應(yīng)變軸。不同圍壓、含水率、干密度下黃土的應(yīng)力應(yīng)變時間效應(yīng)曲線,在不同的時間節(jié)點存在一定差異。參考黃土蠕變特性的Singh-Mitchell模型和Mesri模型以及雙曲線模型對試驗數(shù)據(jù)進行擬合,結(jié)果表明該地區(qū)重塑黃土試樣采用雙曲線模型擬合時,能夠較好的模擬黃土變形規(guī)律,且該模型具有參數(shù)易取,擬合程度較好等優(yōu)點。運用GeoStudio分析軟件,采用試驗擬合的雙曲線模型建立土體變形模量隨時間變化的函數(shù)表達式,分析基坑邊坡黃土在不同偏應(yīng)力作用下豎向應(yīng)變大小隨時間變化情況及應(yīng)力應(yīng)變的時間效應(yīng)曲線特征,并將計算結(jié)果與試驗數(shù)據(jù)進行對比。結(jié)果表明:在不同偏應(yīng)力作用下,基坑邊坡黃土豎向應(yīng)變大小具有明顯的時間效應(yīng),計算軟件采用雙曲線模型能夠較好的擬合試驗數(shù)據(jù),驗證了該模型的準(zhǔn)確性與合理性。
[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.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU444
，
本文編號：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.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU444
，
本文編號：2330482
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