發(fā)布時間：2018-09-13 14:06

【摘要】：瀝青混合料由離散剛性集料和連續(xù)黏性介質(zhì)組成,從體積組成來看,瀝青混合料中集料占絕大部分,約占總體積的90%,屬于典型的顆粒體系。合理的集料體積組成不僅可以改善瀝青混合料的力學性能,也可以協(xié)調(diào)瀝青混合料多相復合材料的復雜行為。從細觀角度上看,集料顆粒隨機地分散在瀝青砂漿介質(zhì)中,顆粒自身的物理力學性質(zhì)、顆粒間嵌擠、摩擦作用等都對瀝青混合料的力學性質(zhì)產(chǎn)生顯著影響。而現(xiàn)有的瀝青混合料設計方法多基于連續(xù)介質(zhì)理論以及宏觀現(xiàn)象學試驗分析方法,忽略了對集料及其細觀結構進行系統(tǒng)的研究與分析。本文借助顆粒物質(zhì)理論,主要利用數(shù)值模擬方法并結合室內(nèi)試驗,對顆粒路面材料細觀結構和力學特性開展研究。首先,基于顆粒物質(zhì)理論,分析集料間的摩擦、接觸、嵌擠等細觀相互作用機制建立了離散集料貫入試驗細觀模擬的PFC3D模型,討論了模型細觀參數(shù)與宏觀貫入力之間的關系,結果表明貫入力對顆粒摩擦系數(shù)和孔隙率的敏感性要遠大于顆粒接觸剛度比,模擬試驗結果與已有的室內(nèi)試驗結果吻合性良好。其次,基于逐級填充理論,建立多級填充的顆粒數(shù)值模型,分析連續(xù)級配和間斷級配集料混合物的力學響應和細觀演化規(guī)律,結合CBR和VCA的指標評價集料骨架嵌擠密實狀態(tài),并提出較優(yōu)的級配組成。最后,統(tǒng)計分析隨機堆積模型得到的初始顆粒體結構,在重力荷載作用下的離散動態(tài)計算以后,單一粒徑散粒體的平均配位數(shù)隨空隙率的減小而增加,混合粒徑球形散粒體的平均配位數(shù)變化范圍很小,基本保持常數(shù),與文獻實測結果吻合,表明文章所提出的數(shù)值計算方法能夠較好的模擬顆粒體在重力場內(nèi)的堆積行為。并在此基礎上,分析貫入試驗過程中集料混合物的細觀力學響應,觀察力鏈結構網(wǎng)絡圖和平均配位數(shù)的變化過程,通過顆粒位移矢量場的變化得到集料顆粒內(nèi)部的遷移演化規(guī)律。研究表明,文章借助PFC3D平臺的研究方法能夠方便有效的觀察顆粒類路面材料堆積行為和骨架穩(wěn)定過程,為進一步研究復雜形狀的顆粒遷移與力鏈穩(wěn)定等行為奠定基礎。
[Abstract]:Asphalt mixture is composed of discrete rigid aggregate and continuous viscous medium. In volume composition, aggregate accounts for most of the asphalt mixture, accounting for about 90% of the total volume, which is a typical particle system. Reasonable aggregate volume composition can not only improve the mechanical properties of asphalt mixture, but also coordinate the complex behavior of multiphase composite material of asphalt mixture. From a meso point of view, aggregate particles are randomly dispersed in the medium of asphalt mortar, the physical and mechanical properties of the particles themselves, intergranular squeezing, friction and so on have a significant impact on the mechanical properties of asphalt mixture. However, most of the existing design methods of asphalt mixture are based on continuum theory and macro phenomenological experimental analysis method, and neglect the systematic research and analysis of aggregate and its mesoscopic structure. In this paper, with the help of particle material theory, numerical simulation method and laboratory test are used to study the microstructure and mechanical properties of granular pavement materials. Firstly, based on the theory of granular matter, the PFC3D model for mesoscopic simulation of discrete aggregate penetration test is established by analyzing the mechanism of mesoscopic interaction such as friction, contact and extrusion between aggregates, and the relationship between the mesoscopic parameters of the model and the macroscopic penetration force is discussed. The results show that the sensitivity of penetration force to particle friction coefficient and porosity is much greater than that of particle contact stiffness ratio. Secondly, based on the theory of step by step filling, the numerical model of multi-stage filling particles is established, and the mechanical response and meso-evolution law of continuous and discontinuous gradation aggregate mixtures are analyzed. Combined with the indexes of CBR and VCA, the compaction state of aggregate skeleton is evaluated. The optimal gradation composition is also proposed. Finally, after statistical analysis of the initial particle structure obtained by the random packing model, after the discrete dynamic calculation under the action of gravity load, the average coordination number of the single particle size particle increases with the decrease of the porosity. The variation range of average coordination number of spherical granular particles with mixed particle size is very small, which is consistent with the measured results in literature. It shows that the numerical calculation method proposed in this paper can well simulate the stacking behavior of particles in the gravity field. On this basis, the mechanical response of aggregate mixture during penetration test is analyzed, and the variation process of the structure network diagram and the average coordination number of the observed force chain is analyzed. The internal migration and evolution of aggregate particles are obtained by the change of particle displacement vector field. The research results show that the method of PFC3D platform can be used to observe the stacking behavior and skeleton stability process of granular pavement materials conveniently and effectively, which lays a foundation for further study on the behavior of particle migration and force chain stability of complex shapes.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U414

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本文編號：2241388