本文選題：尺度效應(yīng)　切入點(diǎn)：顆粒轉(zhuǎn)動(dòng)　出處：《華南理工大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：土體是由跨越多個(gè)數(shù)量級(jí)尺度的礦物顆粒、水和空氣通過(guò)一定方式聚集而成的非連續(xù)顆粒介質(zhì),其宏觀力學(xué)特性與土顆粒尺寸和顆粒運(yùn)動(dòng)行為細(xì)節(jié)密切相關(guān),具有非常顯著的顆粒尺度及轉(zhuǎn)動(dòng)效應(yīng)。但經(jīng)典連續(xù)介質(zhì)力學(xué)建立在宏觀尺度上,無(wú)法表征土顆粒尺度及其轉(zhuǎn)動(dòng);離散力學(xué)方法多針對(duì)單一尺度的均勻顆粒體系且計(jì)算量龐大;而應(yīng)變梯度塑性理論一般適用于金屬材料,能否應(yīng)用于土體介質(zhì)尚待研究。本文通過(guò)土體特性影響試驗(yàn),總結(jié)出顆粒性質(zhì)和顆粒尺度對(duì)土體宏觀力學(xué)性質(zhì)的影響規(guī)律,并利用“基體-增強(qiáng)顆�！卑Y(jié)構(gòu)模型,提出了一種可考慮顆粒尺度和轉(zhuǎn)動(dòng)效應(yīng)的土體彈塑性理論(以下簡(jiǎn)稱“尺度理論”),同時(shí),借助ABAQUS用戶子程序接口二次開發(fā)了相應(yīng)的有限元程序。數(shù)值模擬和理論分析表明,所發(fā)展的有限元方法可較好地解決經(jīng)典彈塑性理論存在的問(wèn)題,合理地預(yù)測(cè)土體變形過(guò)程中因顆粒尺度及轉(zhuǎn)動(dòng)效應(yīng)引起的特殊力學(xué)行為�；谏鲜鲅芯抗ぷ�,取得的成果主要有如下幾個(gè)方面:(1)根據(jù)礦物成分與粒度成分土體特性影響試驗(yàn)總結(jié)顆粒性質(zhì)和顆粒尺度對(duì)土體宏觀力學(xué)性質(zhì)的影響規(guī)律和不同尺度顆粒間的相互作用規(guī)律,并利用“基體-增強(qiáng)顆�！蓖馏w胞元模型,在本構(gòu)關(guān)系中引入表達(dá)顆粒尺度的內(nèi)稟尺度因子和反映轉(zhuǎn)動(dòng)變形的轉(zhuǎn)動(dòng)變量,以及包含內(nèi)稟尺度因子的等效剪應(yīng)變和等效剪應(yīng)力,進(jìn)而基于能量法則和Von Mises屈服準(zhǔn)則進(jìn)行理論推導(dǎo),建立了一種可以考慮顆粒尺度及轉(zhuǎn)動(dòng)效應(yīng)的土體彈塑性理論。(2)借助大型通用商業(yè)有限元軟件ABAQUS所帶的UEL用戶自定義單元子程序接口,二次開發(fā)了基于尺度理論的有限元計(jì)算程序,并采用該程序分析了孔洞應(yīng)力集中問(wèn)題的尺度及轉(zhuǎn)動(dòng)效應(yīng)。通過(guò)與經(jīng)典彈塑性理論有限元計(jì)算結(jié)果對(duì)比,驗(yàn)證了所開發(fā)程序的正確性,揭示出應(yīng)力集中與顆粒尺度和顆粒轉(zhuǎn)動(dòng)的內(nèi)在關(guān)聯(lián)性,從變形機(jī)制上解釋了尺度理論的合理性。(3)利用本文所發(fā)展的尺度理論有限元方法,對(duì)土體軟化和變形局部化現(xiàn)象展開了相應(yīng)的數(shù)值模擬和理論分析,研究表明:土體變形局部化過(guò)程中,尺度理論可較好地解決經(jīng)典彈塑性理論遇到的數(shù)值計(jì)算困難和計(jì)算結(jié)果的嚴(yán)重網(wǎng)格依賴性,并借此進(jìn)一步分析剪切帶的發(fā)生和發(fā)展過(guò)程與顆粒尺度和顆粒轉(zhuǎn)動(dòng)的關(guān)聯(lián)規(guī)律,揭示出由于土體顆粒性特征產(chǎn)生的特殊變形行為和變形機(jī)制。(4)利用本文所發(fā)展的尺度理論有限元方法,對(duì)具有工程尺寸的地基承載力問(wèn)題和邊坡滑動(dòng)問(wèn)題進(jìn)行模擬,實(shí)現(xiàn)了土體軟化非線性變形的全過(guò)程計(jì)算,其結(jié)果表現(xiàn)出與經(jīng)典彈塑性理論不同的土體變形行為。除此之外,還探討了顆粒尺度對(duì)土體變形和荷載特性的影響規(guī)律,并給出考慮顆粒尺度及轉(zhuǎn)動(dòng)效應(yīng)的土體變形和破壞機(jī)制,為今后工程災(zāi)害防治提供理論與數(shù)據(jù)參考。
[Abstract]:Soil mass is a discontinuous granular medium, which is composed of mineral particles that span many orders of magnitude, and water and air gather in a certain way. Its macroscopic mechanical properties are closely related to the size of soil particles and the details of particle motion behavior. But the classical continuum mechanics is based on the macroscopic scale, which can not represent the soil particle size and its rotation, and the discrete mechanics method is mostly aimed at the homogeneous particle system with a single scale and has a large amount of calculation. However, the strain gradient plasticity theory is generally applicable to metal materials, and whether it can be applied to soil media remains to be studied. In this paper, the effects of particle properties and particle size on the macroscopic mechanical properties of soil are summarized through the soil characteristic influence test. Based on the cell structure model of "matrix reinforced particles", a soil elastoplastic theory (hereinafter referred to as "scale theory"), which can consider particle size and rotational effect, is proposed. With the help of ABAQUS user subroutine interface, the corresponding finite element program is developed twice. Numerical simulation and theoretical analysis show that the developed finite element method can solve the problems of classical elastoplastic theory. The special mechanical behavior caused by particle size and rotational effect during soil deformation can be reasonably predicted. The main achievements are as follows: (1) based on the experiments of the influence of mineral composition and particle size composition on soil properties, the effects of particle properties and particle size on the macroscopic mechanical properties of soil and the interaction between particles of different scales are summarized. Using the "matrix reinforced particle" soil cell model, the intrinsic scale factor representing particle size and the rotational variable reflecting rotational deformation are introduced into the constitutive relation, as well as equivalent shear strain and equivalent shear stress including intrinsic scale factor. Then based on the energy law and Von Mises yield criterion, a theoretical derivation is made. In this paper, a soil elastoplastic theory, which can consider particle size and rotational effect, is established. The UEL user-defined element subroutine interface is developed with the help of the large commercial finite element software ABAQUS. The finite element calculation program based on scale theory is developed for the second time, and the scale and rotational effect of the stress concentration problem of holes are analyzed by using the program. The results are compared with the results of finite element calculation based on classical elastic-plastic theory. The correctness of the developed program is verified, and the inherent relationship between stress concentration and particle size and particle rotation is revealed. The rationality of the scale theory is explained from the deformation mechanism.) the scale theory finite element method developed in this paper is used. Numerical simulation and theoretical analysis of soil softening and deformation localization are carried out. The results show that: in the process of soil deformation localization, The scale theory can solve the difficulty of numerical calculation and the serious grid dependence of the results of classical elastic-plastic theory, and further analyze the correlation law between the occurrence and development of shear band and particle size and particle rotation. It is revealed that the special deformation behavior and deformation mechanism caused by the particle characteristics of soil mass are simulated by using the scale theory finite element method developed in this paper, and the problems of bearing capacity of foundation and slope sliding with engineering size are simulated. The calculation of soil softening nonlinear deformation is realized. The results show that the deformation behavior of soil is different from that of classical elastoplastic theory. In addition, the influence of particle size on soil deformation and load characteristics is also discussed. The mechanism of soil deformation and failure considering particle size and rotation effect is also given, which can provide theoretical and data reference for engineering disaster prevention and control in the future.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TU433

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