考虑不同颗粒形状的PFC~(3D)砂土直剪试验模拟研究
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摘要
针对纯圆形颗粒在模拟土工直剪试验中的缺陷,以砂土直剪试验为研究对象,基于PFC~(3D)颗粒流程序,以纯圆颗粒为基本形状进行二次开发,利用FISH语言编程,引入了由pebble构成的块体(clump)单元,建立了哑铃形和椭圆形两种不同颗粒形状的簇颗粒,对纯圆颗粒及簇颗粒进行直剪试验模拟对比,并分析了颗粒初始配位数与内摩擦角的关系以及不同颗粒试样的体积变化规律,从细观上描述了不同形状颗粒的空间活跃程度。结果表明:颗粒形状直接影响着数值模拟的精度,椭圆形颗粒的吻合度最高,哑铃形颗粒次之,圆形颗粒较差,椭圆形颗粒较纯圆颗粒的精度提高了7.05%;簇颗粒的初始配位数相比纯圆颗粒较大,其试样表现出较高的强度和稳定性;颗粒形状对试样体积变化有着显著影响;纯圆颗粒的空间活跃程度较为明显,簇颗粒则相对稳定。该研究可为土工试验模拟在颗粒选择及模拟方法上提供一定的参考。
In order to solve the defects of pure round particles in the simulated direct shear test of soil, the direct shear test of sand is taken as the research object, based on PFC~(3 D) particle flow program, pure round particles are developed for the second time, and a clump unit composed of Pebble is introduced by fish language programming, and two clusters of particles with different particle shapes, dumbbell-shaped and oval, are set up to simulate and compare the direct shear test of pure round particles and cluster particles, and the relationship between the initial coordination number of particles and internal friction angle and the volume change law of different particle samples are analyzed, and particles with different shapes are described from the microscopic point of view. The results show that the shape of particles directly affects the accuracy of numerical simulation, and the oval particles have the highest degree of coincidence, followed by dumbbell-shaped particles, and the round particles are poor, and the accuracy of oval particles is 7.05% higher than that of pure round particles; the initial coordination number of cluster particles is larger than that of pure round particles, and their samples show higher strength and stability; the particle shape has a significant influence on the volume change of the sample; the spatial activity of pure round particles is obvious, while cluster particles are relatively stable. This study can provide some reference for geotechnical test simulation in particle selection and simulation methods.
In order to solve the defects of pure round particles in the simulated direct shear test of soil, the direct shear test of sand is taken as the research object, based on PFC~(3 D) particle flow program, pure round particles are developed for the second time, and a clump unit composed of Pebble is introduced by fish language programming, and two clusters of particles with different particle shapes, dumbbell-shaped and oval, are set up to simulate and compare the direct shear test of pure round particles and cluster particles, and the relationship between the initial coordination number of particles and internal friction angle and the volume change law of different particle samples are analyzed, and particles with different shapes are described from the microscopic point of view. The results show that the shape of particles directly affects the accuracy of numerical simulation, and the oval particles have the highest degree of coincidence, followed by dumbbell-shaped particles, and the round particles are poor, and the accuracy of oval particles is 7.05% higher than that of pure round particles; the initial coordination number of cluster particles is larger than that of pure round particles, and their samples show higher strength and stability; the particle shape has a significant influence on the volume change of the sample; the spatial activity of pure round particles is obvious, while cluster particles are relatively stable. This study can provide some reference for geotechnical test simulation in particle selection and simulation methods.
引文
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[11] 尹小涛,郑亚娜,马双科. 基于颗粒流数值试验的岩土材料内尺度比研究[J].岩土力学,2011,32(4):1211- 1215.
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[13] CLEARY P W. DEM simulation of industrial particle flows: case studies of dragline excavator, mixing in tumblers and centrifugal mils[J]. Powder Technology, 2000, 109(1):83- 104.
[14] MISHRA B K, MEHEROTRA S P. Modeling of particle stratification in jigs by the discrete element method[J]. Minerals Engineering, 1998, 11(6): 511- 522.
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[16] 卢廷浩.土力学[M].北京:高等教育出版社,2010.
[17] 赵仕威,周小文,刘文辉,等.考虑颗粒棱角影响的直剪试验的离散元模拟[J].岩土力学,2015,36(S1):602- 607.
[2] 王泳嘉,邢纪波.离散单元法及其在岩土力学中的应用[M].沈阳:东北工学院出版社,1991.
[3] 赵金凤,严颖,季顺迎.基于离散元模型的土石混合体直剪试验分析[J].固体力学学报,2014,35(2):124- 125.
[4] 贾学明,柴贺军,郑颖人.土石混合料大型直剪试验的颗粒离散元细观力学模拟研究[J].岩土力学, 2010, 31(9) :2695- 2703.
[5] 李爽,刘洋,吴可嘉.砂土直剪试验离散元数值模拟与细观变形机理研究[J].长江科学院院报,2017,34(4):104- 110.
[6] SADEK M A, CHEN Y, LIU J. Simulating shear behavior of a sandy soil under different soil conditions[J]. Journal of Terramechanics, 2011, 48(6):451- 458.
[7] 金磊,曾亚武,叶阳,等.不规则颗粒及其集合体三维离散元建模方法的改进[J].岩土工程学报,2017,39(7):1273- 1281.
[8] 杨杰,韩孝峰.基于PFC的堆石料宏细观参数相关性分析[J].人民长江,2018,49(16):107- 109.
[9] JENSEN R P, BOSSCHER P J, PLESHA M E, et al. DEM simulation of granular media—structure interface: effects of surface roughness and particle shape[J]. International Journal for Numerical & Analytical Methods in Geomechanics, 2015, 23(6):531- 547.
[10] 齐阳,唐新军,李晓庆.粗粒土应力诱发各向异性真三轴试验颗粒流模拟研究[J].岩土工程学报,2015,37(12):2292- 2300.
[11] 尹小涛,郑亚娜,马双科. 基于颗粒流数值试验的岩土材料内尺度比研究[J].岩土力学,2011,32(4):1211- 1215.
[12] 刘海涛,程晓辉. 粗粒土尺寸效应的离散元分析[J].岩土力学,2009,30(S1):287- 292.
[13] CLEARY P W. DEM simulation of industrial particle flows: case studies of dragline excavator, mixing in tumblers and centrifugal mils[J]. Powder Technology, 2000, 109(1):83- 104.
[14] MISHRA B K, MEHEROTRA S P. Modeling of particle stratification in jigs by the discrete element method[J]. Minerals Engineering, 1998, 11(6): 511- 522.
[15] 中华人民共和国水利部.土工试验方法标准:GB/T 50123—1999[S].北京:中国水利水电出版社,1999.
[16] 卢廷浩.土力学[M].北京:高等教育出版社,2010.
[17] 赵仕威,周小文,刘文辉,等.考虑颗粒棱角影响的直剪试验的离散元模拟[J].岩土力学,2015,36(S1):602- 607.