基于三维离散单元法的级配碎石动三轴数值试验研究
发布时间：2018-08-16 18:32
【摘要】：级配碎石是典型的散体材料,具有明显的颗粒性结构特征、非线性力学特性及较大的变异性,物理力学特性复杂,采用连续介质力学理论和常规的室内试验难以从本质上揭示其复杂的物理力学特性、变形及破坏机理,本论文以此为背景开展级配碎石三维动三轴数值试验方法及其应用研究。本文通过新“generate”逻辑生成试件,采用球体和平行粘结模型模拟边界条件与三段压实方法模拟成型,构建了级配碎石动三轴数值试验模型。对比引用文献数据和本文试验结果,证明了PFC5.0-3D软件模型的可靠性;通过分析室内动三轴试验和数值试验结果,证明了数值试验方法的可靠性。通过长期加卸载循环数值试验,建议加卸载次数至少为200次;通过真实颗粒形状和球体分别进行动三轴数值试验,结果表明采用球体无法全面分析材料结构-力学特性,模拟结果误差较大,推荐采用真实颗粒形状进行数值试验研究。根据上述确定的模型参数和试验条件进行数值试验研究,得到如下主要结论:(1)根据单档料粒径试验确定橡胶球层厚与顶墙最大运动速率(1e1m/s),并分析微力学参数对级配碎石动三轴数值试验的影响,结果表明:选取弹性模量在30GPa~40GPa、摩擦系数在0.4~0.6范围内的集料试验结果较好。(2)颗粒组成对级配碎石永久变形的影响分析得出:19~26.5mm及16~19mm粒径主要作为骨架颗粒,体积分数应控制在55%~65%之间;4.75mm粒径作为填充颗粒,体积分数应控制在20%~25%之间;13.2mm和9.5mm粒径作为过渡颗粒,体积分数控制应在20%以内。(3)总结分析动三轴数值试验级配碎石永久变形的细观特征,揭示了级配碎石永久变形的机理,细观特征因素基于级配碎石永久变形影响程度重要性的排序为:空隙率及微应力应变颗粒接触(接触力接触数量)颗粒运动(速度矢量颗粒平移与转动位移矢量颗粒坐标)颗粒结构能量响应。
[Abstract]:Graded crushed stone is a typical granular material with obvious granular structure characteristics, nonlinear mechanical properties and large variability, and complex physical and mechanical properties. It is difficult to reveal its complex physical and mechanical properties, deformation and failure mechanism by using continuum mechanics theory and conventional laboratory tests. In this paper, the three-dimensional dynamic triaxial numerical test method of graded crushed stone and its application are studied in this paper. In this paper, the new "generate" logic is used to generate the specimen, and the boundary conditions and the three-stage compaction method are simulated by using the spherical and parallel bonding models, and the dynamic triaxial numerical test model of graded crushed stone is constructed. The reliability of the PFC5.0-3D software model is proved by comparing the reference data with the experimental results in this paper, and the reliability of the numerical test method is proved by analyzing the results of the indoor dynamic triaxial test and the numerical test. It is suggested that the loading and unloading times should be at least 200 times through the long-term cyclic loading and unloading tests, and the dynamic triaxial numerical tests on the real particle shape and the sphere are carried out respectively. The results show that the material structure and mechanical properties can not be fully analyzed by using the sphere. Because the error of simulation results is large, it is recommended that the real particle shape be used for numerical test. According to the above determined model parameters and experimental conditions, The main conclusions are as follows: (1) according to the single particle size test, the thickness of rubber ball layer and the maximum velocity of movement (1e1m/s) of the top wall are determined, and the effect of micromechanical parameters on the dynamic triaxial test of graded crushed stone is analyzed. The results show that when the elastic modulus is in the range of 30 GPA and 40 GPA and the friction coefficient is in the range of 0.4 ~ 0.6, the experimental results are better. (2) the effect of particle composition on the permanent deformation of graded macadam is analyzed. The results show that the particle size of 16~19mm is mainly used as skeleton particle. The volume fraction should be controlled between 55% and 65% and the particle size of 4.75 mm should be used as the filling particle, and the volume fraction should be controlled between 20% and 25% as the transition particle, and the particle size of 9.5mm should be controlled between 20% and 25%. The control of volume fraction should be within 20%. (3) the characteristics of permanent deformation of graded crushed stone in dynamic triaxial numerical test are summarized and analyzed, and the mechanism of permanent deformation of graded crushed stone is revealed. The order of meso-characteristic factors based on the importance of permanent deformation of graded crushed stone is: void rate and microstress strain particle contact (contact force contact number) particle motion (velocity vector particle translation and rotational displacement vector) Particle coordinates) the energy response of particle structure.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U414
[Abstract]:Graded crushed stone is a typical granular material with obvious granular structure characteristics, nonlinear mechanical properties and large variability, and complex physical and mechanical properties. It is difficult to reveal its complex physical and mechanical properties, deformation and failure mechanism by using continuum mechanics theory and conventional laboratory tests. In this paper, the three-dimensional dynamic triaxial numerical test method of graded crushed stone and its application are studied in this paper. In this paper, the new "generate" logic is used to generate the specimen, and the boundary conditions and the three-stage compaction method are simulated by using the spherical and parallel bonding models, and the dynamic triaxial numerical test model of graded crushed stone is constructed. The reliability of the PFC5.0-3D software model is proved by comparing the reference data with the experimental results in this paper, and the reliability of the numerical test method is proved by analyzing the results of the indoor dynamic triaxial test and the numerical test. It is suggested that the loading and unloading times should be at least 200 times through the long-term cyclic loading and unloading tests, and the dynamic triaxial numerical tests on the real particle shape and the sphere are carried out respectively. The results show that the material structure and mechanical properties can not be fully analyzed by using the sphere. Because the error of simulation results is large, it is recommended that the real particle shape be used for numerical test. According to the above determined model parameters and experimental conditions, The main conclusions are as follows: (1) according to the single particle size test, the thickness of rubber ball layer and the maximum velocity of movement (1e1m/s) of the top wall are determined, and the effect of micromechanical parameters on the dynamic triaxial test of graded crushed stone is analyzed. The results show that when the elastic modulus is in the range of 30 GPA and 40 GPA and the friction coefficient is in the range of 0.4 ~ 0.6, the experimental results are better. (2) the effect of particle composition on the permanent deformation of graded macadam is analyzed. The results show that the particle size of 16~19mm is mainly used as skeleton particle. The volume fraction should be controlled between 55% and 65% and the particle size of 4.75 mm should be used as the filling particle, and the volume fraction should be controlled between 20% and 25% as the transition particle, and the particle size of 9.5mm should be controlled between 20% and 25%. The control of volume fraction should be within 20%. (3) the characteristics of permanent deformation of graded crushed stone in dynamic triaxial numerical test are summarized and analyzed, and the mechanism of permanent deformation of graded crushed stone is revealed. The order of meso-characteristic factors based on the importance of permanent deformation of graded crushed stone is: void rate and microstress strain particle contact (contact force contact number) particle motion (velocity vector particle translation and rotational displacement vector) Particle coordinates) the energy response of particle structure.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U414
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