本文選題：瞬時(shí) + 流變　； 參考：《長(zhǎng)安大學(xué)》2014年博士論文

【摘要】：本文通過(guò)對(duì)大理巖進(jìn)行不同應(yīng)力加載速率下的常規(guī)單軸壓縮試驗(yàn)與不同初始加載應(yīng)力下的單軸蠕變?cè)囼?yàn)，研究了大理巖瞬時(shí)及流變力學(xué)特性，并在其力學(xué)特性基礎(chǔ)上分別研究了考慮應(yīng)力加載速率的瞬時(shí)本構(gòu)模型與大理巖流變本構(gòu)模型。 在瞬時(shí)力學(xué)研究中，作者設(shè)計(jì)了五個(gè)級(jí)別的應(yīng)力加載速率并對(duì)大理巖實(shí)施了各應(yīng)力加載速率下的單軸壓縮試驗(yàn)，分析了不同應(yīng)力加載速率下大理巖變形特征、強(qiáng)度特征、破壞特征及能量交換特征。分析結(jié)果表明，應(yīng)力加載速率的提高對(duì)大理巖的力學(xué)性質(zhì)具有增強(qiáng)效應(yīng)。當(dāng)應(yīng)力加載速率增大時(shí)，，大理巖變形模量增大，強(qiáng)度增大，脆性增強(qiáng)。基于應(yīng)力加載速率對(duì)大理巖力學(xué)性質(zhì)增強(qiáng)效應(yīng)，應(yīng)用統(tǒng)計(jì)損傷力學(xué)與BP神經(jīng)網(wǎng)絡(luò)技術(shù)分別構(gòu)建考慮應(yīng)力加載速率影響的瞬時(shí)本構(gòu)模型。兩種模型各自具有相應(yīng)的優(yōu)點(diǎn)。統(tǒng)計(jì)損傷模型不僅考慮了應(yīng)力加載速率效應(yīng)，同時(shí)從損傷的角度展示了大理巖破壞的機(jī)制。而B(niǎo)P神經(jīng)網(wǎng)絡(luò)模型則具有快速建模且較強(qiáng)的工程實(shí)用性特點(diǎn)。 在大理巖流變力學(xué)研究中，作者首先設(shè)計(jì)并實(shí)施了不同初始加載應(yīng)力，相同加載應(yīng)力增量與相同單級(jí)持續(xù)時(shí)間的單軸分級(jí)加載蠕變?cè)囼?yàn)。蠕變曲線反映了大理巖作為脆性巖石具有的非線性流變特征。通過(guò)對(duì)蠕變曲線的深入分析，總結(jié)了四種具有代表性的大理巖變形方式，并提出了“加速臨界應(yīng)力區(qū)間”、“負(fù)蠕變”及“等速臨界應(yīng)力”等概念，同時(shí)對(duì)其進(jìn)行了初步探討。在對(duì)大理巖蠕變變形的速率特征、長(zhǎng)期強(qiáng)度計(jì)算與特征、破壞特征分析的基礎(chǔ)上總結(jié)了不同的初始加載應(yīng)力對(duì)其變形及破壞具有的影響。其次對(duì)蠕變破壞大理巖斷口與切片進(jìn)行了微細(xì)觀觀察試驗(yàn)，對(duì)破壞斷口的微觀花樣與切片裂紋的展布及形態(tài)進(jìn)行了分析，并在此基礎(chǔ)上對(duì)大理巖蠕變破壞機(jī)制進(jìn)行了探討，得出大理巖蠕變破壞遵循原始裂紋缺陷的加載損傷試樣內(nèi)部非協(xié)調(diào)變形損傷加劇裂紋擴(kuò)展壯大宏觀劈裂伴生剪切破壞的發(fā)展模式。再次，基于分?jǐn)?shù)階微積分理論的數(shù)學(xué)優(yōu)勢(shì)，用分?jǐn)?shù)階微積分構(gòu)建了大理巖流變模型，并應(yīng)用損傷力學(xué)及非線性粘滯理論對(duì)模型進(jìn)行了改進(jìn)，得到了可反映大理巖非線性流變特征的變參數(shù)蠕變損傷模型�；诖罄韼r加速蠕變階段的特點(diǎn)，提出了兩個(gè)非線性粘滯元件，將其與分?jǐn)?shù)階微積分元件聯(lián)合建模，得到了兩個(gè)可反映大理巖整體流變特征的四元件模型�；诹髯儽緲�(gòu)模型實(shí)用性原則，本文從改進(jìn)一種彈塑性體元件入手，聯(lián)合分?jǐn)?shù)階微積分元件，構(gòu)建了一種新的、實(shí)用的及簡(jiǎn)潔的三元件模型。模型經(jīng)過(guò)驗(yàn)證其具有較好的模擬精度與推廣性。最后，基于支持向量機(jī)學(xué)習(xí)技術(shù)的發(fā)展優(yōu)勢(shì)，將其引入巖石流變本構(gòu)模型研究中。在簡(jiǎn)述了支持向量機(jī)特點(diǎn)的基礎(chǔ)上構(gòu)建了分別加載下巖石流變的支持向量機(jī)模型。模型經(jīng)過(guò)驗(yàn)證具有較高的模擬精度與快速工程應(yīng)用特性。
[Abstract]:In this paper, the instantaneous and rheological properties of marble are studied by uniaxial compression tests under different stress loading rates and uniaxial creep tests under different initial loading stresses. On the basis of its mechanical properties, the instantaneous constitutive model and the rheological constitutive model of marble considering the stress loading rate are studied respectively. In the study of instantaneous mechanics, the author designs five levels of stress loading rates and carries out uniaxial compression tests on marble under different stress loading rates, and analyzes the deformation and strength characteristics of marble under different stress loading rates. Damage characteristics and energy exchange characteristics. The results show that the increase of stress loading rate can enhance the mechanical properties of marble. When the stress loading rate increases, the deformation modulus, strength and brittleness of marble increase. Based on the enhancement effect of stress loading rate on the mechanical properties of marble, the statistical damage mechanics and BP neural network technique are used to construct the instantaneous constitutive model considering the effect of stress loading rate respectively. The two models have their respective advantages. The statistical damage model not only considers the effect of stress loading rate, but also shows the mechanism of marble failure from the point of view of damage. The BP neural network model has the characteristics of fast modeling and strong engineering practicability. In the study of rheological mechanics of marble, the author first designed and carried out the creep tests under uniaxial loading with different initial loading stress, the same loading stress increment and the same single stage duration. The creep curve reflects the nonlinear rheological characteristics of marble as brittle rock. Through the deep analysis of creep curves, four typical deformation modes of marble are summarized, and the concepts of "accelerated critical stress interval", "negative creep" and "isokinetic critical stress" are put forward and discussed preliminarily. Based on the analysis of creep deformation rate, long-term strength calculation and failure characteristics of marble, the effects of different initial loading stress on its deformation and failure are summarized. Secondly, the micro-observation tests on the fracture and slice of the creep failure marble are carried out, and the microcosmic pattern of the fracture surface and the distribution and morphology of the crack in the section are analyzed, and the creep failure mechanism of the marble is discussed. It is concluded that the creep failure of marble follows the development model of internal uncoordinated deformation damage in the specimens with original crack defects which exacerbates the crack growth and macrofracturing accompanied by shear failure. Thirdly, based on the mathematical advantages of fractional calculus theory, the rheological model of marble is constructed by fractional calculus, and the damage mechanics and nonlinear viscosity theory are applied to improve the model. The creep damage model with variable parameters can reflect the nonlinear rheological characteristics of marble. Based on the characteristics of accelerated creep stage of marble, two nonlinear viscous elements are proposed, which are combined with fractional calculus element to model two four-element models which can reflect the rheological characteristics of marble as a whole. Based on the principle of practicability of rheological constitutive model, a new, practical and concise three-element model is constructed by improving an elastoplastic element and combining fractional calculus element. The model is proved to be accurate and extensible. Finally, based on the advantages of support vector machine (SVM) learning technology, it is introduced into the study of rock rheological constitutive model. A support vector machine model for rock rheology under loading is constructed on the basis of a brief description of the characteristics of support vector machine (SVM). The model has been proved to have high simulation accuracy and rapid engineering application characteristics.
【學(xué)位授予單位】：長(zhǎng)安大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TU452

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