本文選題：巖石 + 顆粒離散元��； 參考：《西南交通大學》2014年碩士論文

【摘要】：在實際的巖石工程中,很多巖石的宏觀力學參數(shù)及其本構(gòu)關(guān)系都基本由巖石的壓縮實驗獲取。究其原因,傳統(tǒng)觀念認為在大多數(shù)情況下巖石承受的是壓應(yīng)力而并非拉應(yīng)力。目前來講,室內(nèi)實驗對巖石抗拉強度的獲取主要來自于劈裂實驗。但是,劈裂實驗存在的缺陷導致測量的結(jié)果和巖石的真實抗拉強度存在很大的誤差,由此可以看出只有直接拉伸實驗才能真實的正確的反映巖石的抗拉特性。隨著很多重大巖石工程的興建,學者們開始大量的致力于巖石三軸壓縮試驗的研究,并取得了大量成果。但是這些研究大多是從宏觀上探索巖石的力學性能,只有把細觀角度的分析和宏觀力學行為結(jié)合起來才能真實了解巖石力學特性的本質(zhì)。而數(shù)值方法在這些方面的研究表現(xiàn)出了很大的優(yōu)越性。 為了規(guī)避有限元等方法(把巖石視為連續(xù)均勻介質(zhì))在研究巖石拉伸壓縮的力學特性中存在的缺陷,本文采用非連續(xù)介質(zhì)力學研究中的重要數(shù)值模擬方法—顆粒離散元法對巖石的拉伸壓縮實驗進行模擬,從細觀出發(fā)分析巖石的變性破壞機制,以期達到數(shù)值模擬實驗代替或部分代替巖石室內(nèi)試驗的目的。本文利用顆粒流軟件PFC2D進行以下研究： (1)以雙軸壓縮離散元模型的構(gòu)建為例,介紹了顆粒離散元模型的構(gòu)建方法。通過改變單個顆粒細觀參數(shù)的數(shù)值來分析巖石宏觀力學性能的變化,最后總結(jié)得出顆粒離散元模型顆粒之間細觀參數(shù)和巖石宏觀參數(shù)的對應(yīng)關(guān)系。 (2)構(gòu)建砂巖單軸壓縮顆粒離散元模型,通過對砂巖單軸壓縮室內(nèi)試驗的反復(fù)模擬,標定出反映真實砂巖的顆粒間細觀參數(shù)。分析模擬實驗所得應(yīng)力—應(yīng)變曲線、試樣破壞形式及微裂紋發(fā)育情況,探討巖石脆性材料的變形破壞機理。采用標定過的細觀參數(shù)構(gòu)建砂巖的直接拉伸數(shù)值模型,對其應(yīng)力—應(yīng)變曲線及破壞形式進行分析。 (3)采用雙軸壓縮顆粒離散元模型對大理巖室內(nèi)試驗結(jié)果進行標定,獲取能表現(xiàn)大理巖力學特性的顆粒細觀參數(shù)。通過對不同圍壓下三軸數(shù)值試驗獲取的應(yīng)力—應(yīng)變曲線和強度特征進行分析,驗證了數(shù)值試驗結(jié)果與大理巖室內(nèi)試驗結(jié)果模擬的一致性。通過分析數(shù)值試驗的破壞形式及微裂紋的發(fā)育特點,探討了巖石試樣微裂紋的發(fā)育與其變形破壞形式之間的關(guān)系。
[Abstract]:In practical rock engineering, many macroscopic mechanical parameters and constitutive relations of rock are obtained by compression experiments. The reason is that rock is subjected to compressive stress rather than tensile stress in most cases. At present, the tensile strength of rock obtained by laboratory experiments mainly comes from splitting experiments. However, the defects in the splitting experiment lead to great errors between the measured results and the real tensile strength of the rock. It can be seen that only the direct tensile test can truly and correctly reflect the tensile properties of the rock. With the construction of many important rock projects, scholars began to devote themselves to the research of triaxial compression test of rock, and made a lot of achievements. However, most of these studies are to explore the mechanical properties of rocks from a macro perspective. Only by combining the microscopic analysis with the macroscopic mechanical behavior can the nature of rock mechanical properties be truly understood. The numerical method shows great superiority in these aspects. In order to avoid the defects of finite element method (treating rock as a continuous homogeneous medium) in studying the mechanical properties of rock tensile compression, In this paper, an important numerical simulation method in discontinuous medium mechanics, particle discrete element method, is used to simulate the tensile compression experiment of rock, and the mechanism of denaturation and failure of rock is analyzed from the view of meso. In order to achieve the purpose of numerical simulation experiment to replace or partly replace the laboratory test of rock. In this paper, the particle flow software PFC2D is used to carry out the following research: (1) taking the construction of the biaxial compression discrete element model as an example, the method of constructing the particle discrete element model is introduced. The change of macroscopic mechanical properties of rock is analyzed by changing the values of single particle meso parameters. Finally, the corresponding relationship between the mesoscopic parameters and the macroscopic parameters of rock is obtained. (2) the discrete element model of sandstone uniaxial compression particles is constructed, and the simulation of the laboratory test of sandstone uniaxial compression is carried out repeatedly. The meso-grain parameters reflecting the real sandstone are calibrated. The stress-strain curve, failure form of specimen and the development of micro-crack are analyzed, and the deformation and failure mechanism of brittle rock is discussed. The direct tensile numerical model of sandstone is constructed by using the calibrated meso-parameters. The stress-strain curve and failure form are analyzed. (3) the results of laboratory tests of marble are calibrated by using the biaxial compression particle discrete element model. The particle meso parameters which can represent the mechanical properties of marble are obtained. Through the analysis of stress-strain curves and strength characteristics obtained from triaxial numerical tests under different confining pressures, it is verified that the numerical test results are consistent with the simulation results of marble laboratory tests. The relationship between the development of microcracks and the deformation and failure of rock samples is discussed by analyzing the failure form of numerical test and the characteristics of microcrack development.
【學位授予單位】：西南交通大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU45

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