本文選題：堆石體 + 多尺度�。� 參考：《武漢大學》2015年博士論文

【摘要】：高堆石壩建設的快速發(fā)展對堆石體的宏細觀力學特性研究提出了更高要求。堆石體自身的多尺度結構和典型的非線性、非均勻、離散性、各向異性等使得人們對其宏細觀變形機理的認識還不夠深入,現行的本構模型和設計理論還不能完全滿足工程實踐的需求。目前,堆石體應力變形的研究方法主要是采用基于連續(xù)介質模型的有限元方法進行,它能夠在宏觀層面上基本等效地得到堆石體的應力變形特性,但難以反映堆石體在細觀尺度上的演變過程,如顆粒破碎、顆�；频戎匾卣�。離散元或者以離散元為基礎的多尺度數值試驗不受試驗尺寸的限制,并能夠區(qū)分影響堆石體力學性能的各種因素,同時也可以方便地監(jiān)測堆石體內部結構在加載過程中的演化過程,數值試驗的這些優(yōu)勢一方面為研究堆石體的細觀變形機理或宏觀力學特性產生機制提供了新的途徑,另一方面也可為完善堆石體的本構關系提供理論依據。因此,有必要從細觀數值方法入手,以多尺度方法為手段,從宏細觀角度研究堆石體的力學特性。多尺度方法是研究堆石體等復雜顆粒體系的一種有效思路。本文提出了一種分階耦合有限元-離散元的多尺度模擬方法,分析和推導了該多尺度方法中的關鍵關系式,構建了相應計算框架。該多尺度方法采用有限元模擬邊值問題,并從對應于每個高斯積分點的離散顆粒集合體提取本構關系用于整體求解。該方法既能避免傳統連續(xù)方法對基于唯象假定的本構關系的依賴,又能克服單純離散元不能有效模擬大尺度工程問題的缺點,同時還可以將宏觀響應與顆粒材料的細觀機制有效關聯。通過堆石體雙軸壓縮多尺度數值試驗,對堆石顆粒材料的宏細觀特性進行了系統的研究。宏觀力學響應表現出圍壓相關性與非對稱的應變局部化現象；剪切帶內外以及邊緣積分點表現出不同的局部響應；在細觀組構方面,分析了加載過程中配位數的演化規(guī)律、顆粒的運動規(guī)律以及接觸力鏈的發(fā)展,從細觀層次解釋了堆石顆粒體系的力學性質；顆粒集合體的接觸力分布具有非均勻性與空間各向異性,剪切帶內顆粒集合體的主應力發(fā)生了偏轉,各向異性程度更加明顯；分析了各向異性系數的演化過程以及不同各向異性來源對總體各向異性的貢獻權重；研究了加載過程中顆粒集合體能量的演變。隨著表征元顆粒數目的增多,接觸法向的分布越均勻、各向異性程度越小,但在軟化行為的模擬方面有一定差別。數值算例充分展示了該多尺度模擬方法在顆粒材料基本特性研究及其實際工程應用方面良好的運用前景。對隨機散粒體不連續(xù)變形(SGDD)方法中的接觸力學模型、彈塑性應力應變關系、時域離散和積分等方面進行了簡要介紹。以實際工程筑壩料為例,對堆石顆粒形狀進行了分析和模擬,發(fā)展了堆石顆粒隨機生成方法。該算法可生成不同顆粒形狀、不同孔隙率、不同級配的顆粒集合體,在細觀尺度上實現了堆石顆粒幾何形態(tài)與空間分布的精細化描述。在隨機散粒體不連續(xù)變形方法的基礎上,引入內聚力模型,將準脆性材料離散為實體單元與無厚度界面單元,并對界面單元的剛度等參數進行推導,通過界面單元的起裂、擴展和失效,實現了巖體等準脆性材料開裂擴展的數值模擬。該方法能夠顯式地模擬三維顆粒破碎現象,不需要在裂縫尖端重新剖分網格,確保了數值計算的穩(wěn)定性,提高了計算效率。數值模型中,損傷與斷裂只發(fā)生在界面單元上,實體單元僅發(fā)生彈性變形,界面單元的應力狀態(tài)達到破壞準則后,運用基于斷裂能的損傷演化模型,界面單元失效后從模型中刪除,之前由界面單元相連的實體單元轉為接觸狀態(tài)。以巴西劈裂試驗等算例對該方法進行了驗證,較好地模擬了裂紋的開裂萌生與擴展。在分析顆粒破碎力學機制的基礎上,應用該方法模擬了堆石體的顆粒破碎。基于多尺度力學模型與隨機散粒體不連續(xù)變形方法,建立了堆石體的數值試驗平臺。數值試驗平臺能夠模擬剛性或柔性邊界條件,提供位移或應力加載方式,提取顆粒集合體的宏觀力學指標。在詳細闡述數值試驗過程的基礎上,分別研究了堆石體的縮尺效應和錨固效應。以水布埡面板堆石壩主次堆石料為研究對象,建立了考慮顆粒破碎與顆粒強度尺寸效應的散粒體數值模型,重點研究了顆粒強度的尺寸效應以及試樣的尺寸對堆石體力學特性的影響,分析了縮尺后堆石體力學特性的變化規(guī)律。將礫石錨固試驗進行數值實現,分別建立了不同錨桿間距和不同顆粒粒徑的數值試樣,數值模擬結果能夠較好地反映不同加錨散粒體結構的變形規(guī)律與錨固效應,散粒體材料表現出的宏觀特性與其細觀組構的演化密切相關。
[Abstract]:The rapid development of the construction of high rockfill dams has put forward higher requirements for the study of the macro and meso mechanical properties of rockfill. The multi-scale structure of the rockfill body and the typical nonlinear, non-uniform, discrete, anisotropic and so on make people's understanding of its macro and meso deformation mechanism not deep enough, and the existing constitutive model and design theory can not be finished. At present, the research method of stress and deformation of rockfill is mainly based on the finite element method based on continuous medium model. It can basically equivalently obtain the stress and deformation characteristics of rockfill body at the macroscopic level, but it is difficult to reflect the evolution process of rockfill body on the meso scale, such as particle breakage and particle. The multi scale numerical test based on discrete element or discrete element is not limited by the test size, and can distinguish the factors that affect the mechanical properties of the rockfill, and can also conveniently monitor the evolution of the internal structure of the rockfill in the loading process. These advantages of numerical experiments are studied on the one hand. A new way is provided for the mechanism of the meso deformation and the mechanism of macroscopic mechanical properties. On the other hand, it can provide a theoretical basis for improving the constitutive relation of rockfill. Therefore, it is necessary to study the mechanical properties of the rockfill body from the meso scale method by the meso numerical method and the multi scale method. This paper presents a multi-scale simulation method for the multiscale coupled finite element discrete element method, analyzes and derives the key relation in the multiscale method, and constructs the corresponding calculation framework. The multiscale method uses finite element method to simulate the boundary value problem and corresponds to each Gauss. This method can not only avoid the dependence of the traditional continuous method on the constitutive relation based on the phenomenological hypothesis, but also overcome the shortcomings that the simple discrete element can not effectively simulate the large scale engineering problem. At the same time, the macroscopic response and the microscopic mechanism of the granular material can be effective. The macro and mesoscopic characteristics of rockfill particles are systematically studied by the multiscale numerical test of rock mass biaxial compression. The macroscopic mechanical response shows the localized strain localization and the asymmetric strain localization. The local response of the shear zone and the edge integration points shows different local responses; in the meso structure, the analysis is analyzed. The evolution law of the coordination number, the movement law of particles and the development of contact force chain during the loading process, the mechanical properties of the particle system are explained from the meso level. The contact force distribution of the particle aggregate has non uniformity and spatial anisotropy, the main stress of the granular aggregate in the shear zone is deflected, the degree of anisotropy is the degree of anisotropy. It is more obvious that the evolution process of the anisotropy coefficient and the contribution weight of different anisotropy sources to the overall anisotropy are analyzed. The evolution of the energy of the particle aggregate during the loading process is studied. With the increase of the number of particles, the more uniform distribution of the contact method and the smaller the anisotropy, but the modulus of the softening behavior. The numerical examples fully demonstrate the good application prospect of the multi-scale simulation method in the research of the basic properties of granular materials and the practical engineering applications. The contact mechanics model, the elastic plastic stress stress stress relation, the time domain discrete and integral in the random granular discontinuous deformation (SGDD) method are carried out. Taking the actual engineering damming materials as an example, the shape of rockfill particles is analyzed and simulated, and the random generation method of rockfill particles has been developed. This algorithm can generate particles with different particle shapes, different porosity and different gradations, and the fine description of the geometric shape and spatial distribution of rockfill particles is realized on the meso scale. On the basis of the random granular discontinuous deformation method, the cohesive force model is introduced to discrete the quasi brittle material into the solid element and the non thickness interface element, and the stiffness and other parameters of the interface element are derived. Through the initiation, expansion and failure of the interface unit, the numerical simulation of the crack propagation of the quasi brittle materials, such as rock body, is realized. The method can be used to simulate the three-dimensional particle breakage clearly. It does not need to re divide the mesh at the tip of the crack, which ensures the stability of the numerical calculation and improves the calculation efficiency. In the numerical model, the damage and fracture only occur on the interface unit, the solid element only takes place elastic deformation, and the stress state of the interface unit reaches the failure criterion, and the application base is used. In the damage evolution model of fracture energy, the interface unit is deleted from the model after failure, and the solid element connected by the interface unit is turned into contact state before the failure. The method is verified by the example of Brazil splitting test, and the crack initiation and propagation are simulated well. On the basis of the analysis of the mechanical mechanism of the particle breakage, the application of this method is used. This method simulates the particle breakage of rockfill. Based on the multi scale mechanical model and the random granular discontinuous deformation method, the numerical test platform of the rockfill body is established. The numerical test platform can simulate the rigid or flexible boundary conditions, provide the displacement or stress loading mode and extract the macroscopic mechanical indexes of the grain aggregate. On the basis of the numerical test process, the scale effect and the anchorage effect of the rockfill body are studied. The bulk material model of the primary and secondary piles of the Shuibuya concrete face rockfill dam is taken as the research object. The size effect of the particle size and the size effect of the particle strength is established. The size effect of the particle strength and the size of the specimen to the rockfill body are studied. The change law of mechanical properties of the rockfill body after the scale is analyzed. The numerical realization of the gravel anchorage test is carried out, and the numerical samples with different bolt spacing and different particle size are set up respectively. The numerical simulation results can better reflect the deformation law and anchorage effect of different anchorage granular structures. The macroscopic characteristics are closely related to the evolution of meso structure.

【學位授予單位】：武漢大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TV41

【參考文獻】

相關期刊論文 前10條

1 秦尚林;楊蘭強;高惠;陳善雄;;不同應力路徑下絹云母片巖粗粒料聲發(fā)射特征[J];巖土力學;2015年01期

2 周博;黃潤秋;汪華斌;王劍鋒;;基于離散元法的砂土破碎演化規(guī)律研究[J];巖土力學;2014年09期

3 A.Lisjak;G.Grasselli;;A review of discrete modeling techniques for fracturing processes in discontinuous rock masses[J];Journal of Rock Mechanics and Geotechnical Engineering;2014年04期

4 孔憲京;劉京茂;鄒德高;付猛;;紫坪鋪面板壩堆石料顆粒破碎試驗研究[J];巖土力學;2014年01期

5 王長兵;袁會娜;張丙印;張其光;;考慮壩料初始壓密特性的土石壩變形計算方法[J];水利學報;2013年10期

6 張建銀;李光勇;;水布埡面板堆石壩壩體沉降變形規(guī)律分析[J];水電與新能源;2013年05期

7 王永明;朱晟;任金明;彭鵬;徐學勇;;筑壩粗粒料力學特性的縮尺效應研究[J];巖土力學;2013年06期

8 萬柯;李錫夔;;Biot-Cosserat連續(xù)體-離散顆粒集合體模型的非飽和土連接尺度方法[J];應用力學學報;2013年03期

9 邵磊;遲世春;張勇;陶警圓;;基于顆粒流的堆石料三軸剪切試驗研究[J];巖土力學;2013年03期

10 馬剛;周偉;常曉林;周創(chuàng)兵;;堆石料縮尺效應的細觀機制研究[J];巖石力學與工程學報;2012年12期

相關博士學位論文 前2條

1 劉其鵬;基于平均場理論的顆粒材料離散顆粒集合-Cosserat連續(xù)體模型多尺度模擬[D];大連理工大學;2010年

2 楚錫華;顆粒材料的離散顆粒模型與離散—連續(xù)耦合模型及數值方法[D];大連理工大學;2006年

相關碩士學位論文 前1條

1 黃劉剛;內聚力模型的分析及有限元子程序開發(fā)[D];鄭州大學;2010年

，

本文編號：1816134