岩石拉压实验的颗粒离散元模拟

发布时间：2018-07-11 13:52

本文选题：岩石 + 颗粒离散元　；参考：《西南交通大学》2014年硕士论文

【摘要】：在实际的岩石工程中,很多岩石的宏观力学参数及其本构关系都基本由岩石的压缩实验获取。究其原因,传统观念认为在大多数情况下岩石承受的是压应力而并非拉应力。目前来讲,室内实验对岩石抗拉强度的获取主要来自于劈裂实验。但是,劈裂实验存在的缺陷导致测量的结果和岩石的真实抗拉强度存在很大的误差,由此可以看出只有直接拉伸实验才能真实的正确的反映岩石的抗拉特性。随着很多重大岩石工程的兴建,学者们开始大量的致力于岩石三轴压缩试验的研究,并取得了大量成果。但是这些研究大多是从宏观上探索岩石的力学性能,只有把细观角度的分析和宏观力学行为结合起来才能真实了解岩石力学特性的本质。而数值方法在这些方面的研究表现出了很大的优越性。为了规避有限元等方法(把岩石视为连续均匀介质)在研究岩石拉伸压缩的力学特性中存在的缺陷,本文采用非连续介质力学研究中的重要数值模拟方法—颗粒离散元法对岩石的拉伸压缩实验进行模拟,从细观出发分析岩石的变性破坏机制,以期达到数值模拟实验代替或部分代替岩石室内试验的目的。本文利用颗粒流软件PFC2D进行以下研究： (1)以双轴压缩离散元模型的构建为例,介绍了颗粒离散元模型的构建方法。通过改变单个颗粒细观参数的数值来分析岩石宏观力学性能的变化,最后总结得出颗粒离散元模型颗粒之间细观参数和岩石宏观参数的对应关系。 (2)构建砂岩单轴压缩颗粒离散元模型,通过对砂岩单轴压缩室内试验的反复模拟,标定出反映真实砂岩的颗粒间细观参数。分析模拟实验所得应力—应变曲线、试样破坏形式及微裂纹发育情况,探讨岩石脆性材料的变形破坏机理。采用标定过的细观参数构建砂岩的直接拉伸数值模型,对其应力—应变曲线及破坏形式进行分析。 (3)采用双轴压缩颗粒离散元模型对大理岩室内试验结果进行标定,获取能表现大理岩力学特性的颗粒细观参数。通过对不同围压下三轴数值试验获取的应力—应变曲线和强度特征进行分析,验证了数值试验结果与大理岩室内试验结果模拟的一致性。通过分析数值试验的破坏形式及微裂纹的发育特点,探讨了岩石试样微裂纹的发育与其变形破坏形式之间的关系。
[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.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45

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