【摘要】：土的本構(gòu)關(guān)系以土的應(yīng)力應(yīng)變規(guī)律作為研究對象,是巖土工程學(xué)科的重要理論基礎(chǔ),為巖土工程的分析和設(shè)計提供理論依據(jù)和指導(dǎo)。砂性土在我國有著廣泛的分布,針對其基本的力學(xué)特性,國內(nèi)外的學(xué)者已開展了許多相關(guān)的研究,建立了各種各樣的本構(gòu)模型。近幾十年,許多新型的水利電力工程、高層建筑和交通工程如雨后春筍,同時也帶來了許多新的巖土工程問題,如砂土的纖維加筋硬化問題和循環(huán)累積變形問題。福建標(biāo)準(zhǔn)砂是我國的一種代表性試驗用砂,本文針對砂土的纖維加筋硬化問題和循環(huán)累積變形問題,開展了一系列福建標(biāo)準(zhǔn)砂靜動力三軸試驗,研究了福建標(biāo)準(zhǔn)砂的纖維加筋和循環(huán)累積變形特性,并在此基礎(chǔ)上分別建立了相關(guān)的砂土本構(gòu)模型。 纖維加筋是一種新型的土體改良技術(shù),建立纖維加筋土的應(yīng)力應(yīng)變關(guān)系及相關(guān)的力學(xué)模型,不僅有利于纖維加筋土強(qiáng)度和變形特性的預(yù)測,而且也能為纖維加筋土的工程設(shè)計提供參考依據(jù)。而目前纖維加筋土的力學(xué)模型及計算理論研究一直是該領(lǐng)域的研究弱項。本文將纖維加筋土考慮為基本相和纖維相的組合體,分別采用修正劍橋模型和線彈性模型,考慮了大應(yīng)變時纖維加筋土的屈服,引入了加筋土的合理強(qiáng)度模型作為破壞準(zhǔn)則,從而建立了纖維加筋土的一種兩相本構(gòu)模型。同時,開展了纖維體積含量為1%的加筋砂的三軸固結(jié)排水剪切試驗,對該兩相本構(gòu)模型進(jìn)行了驗證。 近幾年,近海風(fēng)電產(chǎn)業(yè)的發(fā)展十分迅速。海上風(fēng)電機(jī)組基礎(chǔ)經(jīng)常受到風(fēng)、波浪、水流甚至地震等循環(huán)荷載的作用。長期的循環(huán)往復(fù)荷載的作用下,基礎(chǔ)往往會產(chǎn)生循環(huán)累積變形,從而影響到海上風(fēng)電機(jī)組的正常運(yùn)行。本文開展了一系列飽和砂土的排水條件單向循環(huán)三軸壓縮和拉伸試驗,研究了動應(yīng)力水平、初始平均應(yīng)力、初始靜應(yīng)力比、初始密實(shí)度對福建標(biāo)準(zhǔn)砂的循環(huán)累積變形特性的影響,發(fā)現(xiàn)動應(yīng)力、初始平均應(yīng)力和初始靜應(yīng)力比越大,初始密實(shí)度越小,砂土的循環(huán)累積變形越大。之后對循環(huán)三軸試驗的數(shù)據(jù)進(jìn)行了分析,得到了軸向循環(huán)累積應(yīng)變和循環(huán)次數(shù)之間的雙對數(shù)線性關(guān)系,將所有影響因素包含于第一次軸向循環(huán)累積應(yīng)變。分析了第一次軸向循環(huán)累積應(yīng)變與初始平均應(yīng)力和偏應(yīng)力水平之間的關(guān)系。最后基于合理的軟黏土循環(huán)累積變形計算模型,對其中的偏應(yīng)力水平的定義進(jìn)行了適當(dāng)?shù)匦拚?并引入與密實(shí)度相關(guān)的砂土抗剪強(qiáng)度理論,建立了飽和砂土的循環(huán)累積變形顯式計算模型,并利用循環(huán)三軸試驗的數(shù)據(jù)對其進(jìn)行了驗證。
[Abstract]:The constitutive relation of soil takes the stress-strain law of soil as the object of study. It is an important theoretical basis of geotechnical engineering and provides theoretical basis and guidance for the analysis and design of geotechnical engineering. Sand soils are widely distributed in China. According to their basic mechanical properties, scholars at home and abroad have carried out many related studies and established various constitutive models. In recent decades, many new water conservancy and electric power projects, high-rise buildings and traffic projects have sprung up, at the same time, many new geotechnical engineering problems have been brought, such as fiber reinforced hardening of sand and cyclic cumulative deformation. Fujian standard sand is a representative test sand in China. A series of static and dynamic triaxial tests of Fujian standard sand have been carried out in this paper, aiming at the problem of fiber reinforced hardening and cyclic cumulative deformation of sand. The properties of fiber reinforcement and cyclic cumulative deformation of Fujian standard sand were studied. Fiber reinforced soil is a new soil improvement technology. The establishment of stress-strain relationship and related mechanical model of fiber reinforced soil is not only beneficial to predict the strength and deformation characteristics of fiber reinforced soil. It can also provide reference for the engineering design of fiber reinforced soil. At present, the research on mechanical model and calculation theory of fiber reinforced soil is always weak in this field. In this paper, the fiber reinforced soil is considered as the combination of basic phase and fiber phase. The modified Cambridge model and the linear elastic model are used to consider the yield of the fiber reinforced soil when the strain is large, and the reasonable strength model of the reinforced soil is introduced as the failure criterion. Thus a two-phase constitutive model of fiber reinforced soil is established. At the same time, the triaxial consolidation and drainage shear tests of reinforced sand with fiber volume of 1% were carried out, and the two-phase constitutive model was verified. In recent years, offshore wind power industry is developing very rapidly. The foundation of offshore wind turbine is often subjected to cyclic loads such as wind, wave, current and even earthquake. Under the action of long term cyclic reciprocating load, the foundation will often produce cyclic cumulative deformation, which will affect the normal operation of offshore wind turbine. In this paper, a series of unidirectional cyclic triaxial compression and tensile tests of saturated sand have been carried out. The dynamic stress level, initial average stress and initial static stress ratio have been studied. The effect of initial compactness on cyclic cumulative deformation of Fujian standard sand shows that the larger the ratio of dynamic stress, initial mean stress and initial static stress, the smaller the initial compactness, the greater the cyclic cumulative deformation of sand. Then, the data of cyclic triaxial test are analyzed, and the logarithmic linear relationship between axial cyclic cumulative strain and cyclic number is obtained, and all the influencing factors are included in the first axial cyclic cumulative strain. The relationship between the first axial cyclic cumulative strain and the initial average stress and deflection stress level is analyzed. Finally, based on the reasonable calculation model of cyclic cumulative deformation of soft clay, the definition of deflection stress level is modified appropriately, and the theory of sand shear strength related to compactness is introduced. An explicit model of cyclic cumulative deformation of saturated sand is established and verified by cyclic triaxial test.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU411;TU441

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本文編號：2390659