本文選題：材料特性相關(guān)塑性位勢理論 + 砂土　； 參考：《寧夏大學(xué)》2017年碩士論文

【摘要】：土體在地震、交通及波浪荷載等復(fù)雜受力條件下,主應(yīng)力軸相對土體會發(fā)生不同程度的旋轉(zhuǎn),該條件下土體應(yīng)力應(yīng)變關(guān)系描述始終是工程界、學(xué)術(shù)界研究的熱點(diǎn)和難點(diǎn)問題。現(xiàn)有土體本構(gòu)關(guān)系絕大部分都在連續(xù)介質(zhì)力學(xué)的理論框架下建立,該理論框架采用了材料為各向同性的假設(shè),當(dāng)材料為各向同性時,主應(yīng)力軸旋轉(zhuǎn)對材料的本構(gòu)關(guān)系無任何影響,這個假設(shè)對描述土體在主應(yīng)力軸旋轉(zhuǎn)條件下的應(yīng)力應(yīng)變關(guān)系帶來了巨大挑戰(zhàn)。砂土在自然形成過程中,顆粒會沿某一方向定向排列,表現(xiàn)出原生各向異性,在復(fù)雜應(yīng)力條件下,顆粒空間排列會發(fā)生演化,表現(xiàn)出明顯的應(yīng)力誘發(fā)各向異性,這種條件下明顯加劇了其應(yīng)力應(yīng)變關(guān)系描述的復(fù)雜性。為此,本文在課題組提出的材料特性相關(guān)塑性位勢理論的基礎(chǔ)上,考慮到砂土細(xì)觀組構(gòu)對其力學(xué)特性的影響,建立砂土的土體本構(gòu)模型,根據(jù)現(xiàn)有單剪試驗(yàn)結(jié)果,從單剪的應(yīng)力應(yīng)變關(guān)系描述、剪脹方程和三維主空間考慮主應(yīng)力旋轉(zhuǎn)的應(yīng)力應(yīng)變關(guān)系描述開展研究,最后,又用PFC軟件對單剪試驗(yàn)進(jìn)行模擬。主要內(nèi)容如下:1、針對單剪試驗(yàn)應(yīng)力應(yīng)變特點(diǎn),推導(dǎo)了該應(yīng)力條件下的砂土的本構(gòu)描述方程,并進(jìn)行了試驗(yàn)?zāi)M。根據(jù)單剪試驗(yàn)主應(yīng)力軸發(fā)生旋轉(zhuǎn)的特點(diǎn),將組構(gòu)張量引入砂土屈服方程中,描述該應(yīng)力條件下細(xì)觀組構(gòu)對砂土屈服函數(shù)的影響;根據(jù)材料狀態(tài)砂土對臨界狀態(tài)線的影響規(guī)律,將新定義的各向異性狀態(tài)變量引入臨界狀態(tài)方程,描述細(xì)觀組構(gòu)對其臨界狀態(tài)的影響;在基于材料特性相關(guān)塑性位勢理論建立砂土的本構(gòu)模型;最后,基于單剪試驗(yàn)結(jié)果,對給試驗(yàn)條件下的應(yīng)力應(yīng)變及應(yīng)力與非共軸角之間的關(guān)系進(jìn)行了模擬,并與實(shí)驗(yàn)結(jié)果進(jìn)行了比較分析。2、基于材料特性相關(guān)塑性位勢理論,結(jié)合單剪試驗(yàn),采用能量轉(zhuǎn)換原理推導(dǎo)了砂土的應(yīng)力剪脹方程。根據(jù)單剪試驗(yàn)過程中的主應(yīng)力軸旋轉(zhuǎn)特點(diǎn),通過材料特性相關(guān)塑性位勢理論計(jì)算主應(yīng)力軸旋轉(zhuǎn)過程中主應(yīng)變增量變化角的關(guān)系,用主應(yīng)力旋轉(zhuǎn)角和對應(yīng)主應(yīng)變旋轉(zhuǎn)角的差值定義非共軸性參數(shù)c,用該參數(shù)描述主應(yīng)力軸旋轉(zhuǎn)條件下材料參數(shù)對砂土剪脹關(guān)系的影響;結(jié)合材料相關(guān)特性理論的剪賬方程進(jìn)行對比,分析單剪試驗(yàn)條件下將松砂、中密砂及密砂的主應(yīng)力旋轉(zhuǎn)角、非共軸參數(shù)與剪賬性的特點(diǎn)。3、使用PFC商業(yè)程序,用離散元模擬單剪試驗(yàn)條件下應(yīng)力應(yīng)變關(guān)系和剪賬關(guān)系。根據(jù)單剪試驗(yàn)條件確定離散元初始加載條件,分析球形顆粒在不同圍壓,不同孔隙率和不同顆粒半徑等排列條件下應(yīng)力應(yīng)變關(guān)系,并且分析其力鏈分布規(guī)律。
[Abstract]:Under the complex loading conditions such as earthquake, traffic and wave loads, the principal stress axis rotates to different degrees relative to the soil mass. Under this condition, the stress-strain relationship description of soil is always a hot and difficult problem in engineering and academic circles. Most of the existing constitutive relations of soil are established under the theoretical framework of continuum mechanics, which adopts the assumption that the material is isotropic, when the material is isotropic. The rotation of the principal stress axis has no effect on the constitutive relationship of the material. This assumption poses a great challenge to describe the stress-strain relationship of soil under the rotation of the principal stress axis. In the process of natural formation of sand, particles will be arranged in a certain direction, showing primary anisotropy. Under complex stress conditions, particle space arrangement will evolve, showing obvious stress-induced anisotropy. Under this condition, the complexity of the stress-strain relationship is obviously increased. Therefore, on the basis of the theory of plastic potential related to material characteristics proposed by the research group, considering the influence of the meso-fabric of sand on its mechanical properties, the constitutive model of soil mass of sand is established, and according to the results of single shear test, the constitutive model of sandy soil is established. In this paper, the stress-strain relation of single shear is described, the expansion equation of shear and the stress-strain relation of three dimensional principal space considering the rotation of principal stress are studied. Finally, the single shear test is simulated by PFC software. The main contents are as follows: 1. According to the stress-strain characteristics of single shear test, the constitutive equation of sand under this stress condition is derived, and the experimental simulation is carried out. According to the characteristics of rotation of principal stress axis in single shear test, the fabric Zhang Liang is introduced into the yield equation of sandy soil to describe the effect of mesoscopic fabric on the yield function of sandy soil under the stress condition, and according to the influence law of sand and soil in material state on critical state line, The newly defined anisotropic state variable is introduced into the critical state equation to describe the influence of mesoscopic fabric on the critical state. The constitutive model of sand is established based on the plastic potential theory related to the material properties. Finally, based on the results of single shear test, The stress-strain and the relationship between stress and non-coaxial angle under experimental conditions are simulated and compared with the experimental results. Based on the theory of plastic potential related to the material properties and the single shear test, the stress strain and the relationship between the stress and the non-coaxial angle are simulated and compared with the experimental results. Based on the principle of energy conversion, the stress-shear expansion equation of sand is derived. According to the rotation characteristics of principal stress axis in the process of single shear test, the relationship between principal strain increment and variation angle during rotation of principal stress axis is calculated by the theory of material characteristic correlation plastic potential. The non-coaxial parameter c is defined by the difference between the rotation angle of principal stress and the rotation angle of corresponding principal strain, and the influence of material parameters on the shear expansion of sand under the rotating condition of principal stress axis is described. Comparing with the shearing equation of material related property theory, this paper analyzes the principal stress rotation angle of loose sand, middle dense sand and dense sand under the condition of single shear test, and the characteristics of non-coaxial parameters and shearing property. The commercial program of PFC is used to analyze the main stress rotation angle, non-coaxial parameter and shearing property of loose sand, middle dense sand and dense sand. The stress-strain relation and shear account relation under single shear test are simulated by discrete element method. The initial loading conditions of discrete elements are determined according to the single shear test conditions. The stress-strain relationships of spherical particles under different confining pressures, different porosity and different particle radius are analyzed, and the force chain distribution is analyzed.
【學(xué)位授予單位】：寧夏大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU43

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