【摘要】：顆粒物質(zhì)是在自然界和工程建設(shè)中廣泛存在的一種物質(zhì)類型，近百年來(lái)得到了廣泛而深入地研究。顆粒物質(zhì)在形成過(guò)程中內(nèi)部形成不同的細(xì)觀組織結(jié)構(gòu)，這些細(xì)觀結(jié)構(gòu)對(duì)體系的整體穩(wěn)定性產(chǎn)生巨大影響。從顆粒角度出發(fā)，研究顆粒接觸形成的細(xì)觀結(jié)構(gòu)（如力鏈網(wǎng)絡(luò)）、動(dòng)力學(xué)過(guò)程及其與宏觀力學(xué)性質(zhì)之間關(guān)系是細(xì)觀研究的主要思路，，這方面工作是工程建設(shè)及地質(zhì)散體災(zāi)害防治關(guān)鍵技術(shù)的理論基礎(chǔ)。 通過(guò)光彈實(shí)驗(yàn)方法可以觀察二維靜力觸探試驗(yàn)過(guò)程中力鏈網(wǎng)絡(luò)的演化規(guī)律。利用圖形處理和基于條紋光強(qiáng)梯度的擬合方法，獲取實(shí)驗(yàn)過(guò)程中顆粒圓心位置，以及顆粒所受力的大小，得到加載過(guò)程中內(nèi)部力鏈網(wǎng)絡(luò)的形態(tài)。采用顆粒流商業(yè)軟件PFC (Particle Flow Code)對(duì)相同加載條件下的顆粒試樣進(jìn)行了數(shù)值模擬，所得結(jié)果與光彈實(shí)驗(yàn)中觀察到的力鏈網(wǎng)絡(luò)吻合較好。分析表明，顆粒體系在外荷載作用下內(nèi)部存在著形態(tài)各異的力鏈網(wǎng)絡(luò)，力鏈網(wǎng)絡(luò)的主要分布方向與體系主應(yīng)力的方向相同，在外荷載作用下力鏈網(wǎng)絡(luò)呈現(xiàn)復(fù)雜的局部化行為。 文章的重點(diǎn)是，提出了基于單顆粒的非仿射應(yīng)變率的概念，來(lái)量化局部化行為。分析了雙軸壓縮、靜力觸探、混凝土立方體抗壓強(qiáng)度以及混凝土圓盤劈拉試驗(yàn)過(guò)程中內(nèi)部非仿射應(yīng)變率的空間分布；利用小波方法分析了非仿射應(yīng)變率較大顆粒的空間關(guān)聯(lián)；引入統(tǒng)計(jì)的概念，建立非仿射應(yīng)變率概率分布演化方程，利用這個(gè)演化方程很好的描述了雙軸壓縮試驗(yàn)過(guò)程中局部化的演化過(guò)程。 將離散元（Discrete Element Method, DEM）串行程序引入并行自適應(yīng)結(jié)構(gòu)網(wǎng)格應(yīng)用支撐軟件框架（J Adaptive Structured Mesh applications Infrastructure,Jasmin），開展了顆粒物質(zhì)大規(guī)模并行數(shù)值模擬，計(jì)算了顆粒膨脹過(guò)程和三軸壓縮試驗(yàn)，分析了力鏈網(wǎng)絡(luò)、局部體積分?jǐn)?shù)、局部應(yīng)力等參數(shù)的不均勻化。數(shù)值模擬結(jié)果顯示，顆粒體系內(nèi)部存在著很強(qiáng)的局部化現(xiàn)象，通過(guò)后處理程序，可以很清晰的觀察顆粒體系內(nèi)部的局部化現(xiàn)象，且隨著體系越來(lái)越密實(shí)，內(nèi)部不均勻性逐漸下降。同時(shí)，我們發(fā)現(xiàn)當(dāng)顆粒體系在達(dá)到堵塞（Jamming）狀態(tài)之后，邊壁壓力增量、配位數(shù)增量以及平均局部應(yīng)力與體積分?jǐn)?shù)的增量形成很好的指數(shù)關(guān)系。
[Abstract]:Granular matter is a kind of material widely existing in nature and engineering construction, which has been studied extensively and deeply in the last hundred years. In the process of the formation of granular matter, different microstructures are formed, which have a great influence on the overall stability of the system. From the point of view of particles, the main idea of mesoscopic research is to study the meso-structure (such as force chain network) formed by particle contact, and the dynamic process and its relationship with macroscopic mechanical properties. This work is the theoretical basis of engineering construction and the key technology of geological bulk disaster prevention. The evolution of the force chain network during the two dimensional static penetration test can be observed by the photoelastic experimental method. By using the graphic processing and fitting method based on the fringe intensity gradient, the position of the center of the particle and the size of the force acting on the particle during the experiment are obtained, and the shape of the internal force chain network during the loading process is obtained. The particle flow commercial software PFC (Particle Flow Code) is used to simulate the particle samples under the same loading conditions. The results are in good agreement with the force chain network observed in the photoelastic experiments. The analysis shows that there are different forms of force chain network in particle system under external load, and the main distribution direction of force chain network is the same as that of system principal stress, and the force chain network presents complex localization behavior under external load. The emphasis of this paper is that the concept of non-affine strain rate based on single particle is proposed to quantify the localization behavior. The spatial distribution of biaxial compression, static penetration, concrete cube compressive strength and internal non-affine strain rate during splitting tensile test of concrete disk is analyzed, and the spatial correlation of large non-affine strain rate particles is analyzed by wavelet method. By introducing the concept of statistics, the evolution equation of probability distribution of non-affine strain rate is established. The evolution process of localization in biaxial compression test is well described by using this evolution equation. The discrete element (Discrete Element Method, DEM) serial program is introduced into the parallel adaptive grid application support software framework (J Adaptive Structured Mesh applications Infrastructure Jasmin). A large-scale parallel numerical simulation of granular matter is carried out, and the particle expansion process and triaxial compression test are calculated. The inhomogeneity of some parameters, such as force chain network, local volume fraction and local stress, is analyzed. The numerical simulation results show that there is a strong localization phenomenon in the particle system. Through the post-processing program, the localization phenomenon in the particle system can be observed clearly, and as the system becomes more and more dense, The internal inhomogeneity decreases gradually. At the same time, we find that the increment of side wall pressure, coordination number, average local stress and volume fraction have a good exponential relationship when the particle system reaches the (Jamming) state.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：O347.7;TU4

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