南京粉细砂空间孔隙结构表征单元体确定
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摘要
确定统一的表征单元体(REV)尺寸是研究土体细观孔隙结构时首先需要解决的问题。使用6.5μm分辨率同步辐射显微CT扫描南京粉细砂试样,从土样三维重构模型的5个代表性部位提取5组立方体孔隙REV,对每个REV采用最大球算法分析,建立孔隙网络模型,从中提取孔隙率、单位体积孔隙数、孔隙平均体积、孔隙最小体积、孔隙最大半径、孔隙最小半径、孔隙平均半径、孔隙截面积平均形状因子等8个孔隙结构参数,建立其与REV尺寸间的相关性。利用假设检验T检验和F检验,最终确定样品孔隙结构参数的统一REV边长尺寸为400像素,即2.60mm。该方法可用于砂土、粉土等颗粒土体细观孔隙结构分析。
Determining the unified representative element volume(REV) is the primary issue to be solved when studying the meso-scale pore structure of soils. We use the synchrotron radiation μ-CT, in 6.5 μm voxel resolution, to scan a Nanjing silty-fine sand specimen. Five groups of cubic pore REV with the same dimension are chosen from the three-dimensional reconstruction model, at different heights, of the specimen. The maximal ball algorithm is used to analyze each pore REV. The pore network model of each REV is developed to extract eight pore structure parameters, namely porosity, pore number per unit volume, mean volume of pore, minimum pore volume, maximal pore radius, minimal pore radius, mean radius of pore and average shape factor of pore area. Subsequently, the correlations between the eight pore structure parameters and the REV size are established respectively. The results show that all the pore structure parameters tend to converge when the REV size increases. The T test and F test are performed with different REV edge lengths for the eight pore structure parameters in sequence. The REV edge length of each pore structure parameters is determined and the maximal value of them is selected. Finally, unified REV edge length is determined at 400 voxels, namely 2.60 mm, for all the pore structure parameters. This determination method can be used for the meso-scale pore structure analysis of grain soils such as sand soil and silty soil.
Determining the unified representative element volume(REV) is the primary issue to be solved when studying the meso-scale pore structure of soils. We use the synchrotron radiation μ-CT, in 6.5 μm voxel resolution, to scan a Nanjing silty-fine sand specimen. Five groups of cubic pore REV with the same dimension are chosen from the three-dimensional reconstruction model, at different heights, of the specimen. The maximal ball algorithm is used to analyze each pore REV. The pore network model of each REV is developed to extract eight pore structure parameters, namely porosity, pore number per unit volume, mean volume of pore, minimum pore volume, maximal pore radius, minimal pore radius, mean radius of pore and average shape factor of pore area. Subsequently, the correlations between the eight pore structure parameters and the REV size are established respectively. The results show that all the pore structure parameters tend to converge when the REV size increases. The T test and F test are performed with different REV edge lengths for the eight pore structure parameters in sequence. The REV edge length of each pore structure parameters is determined and the maximal value of them is selected. Finally, unified REV edge length is determined at 400 voxels, namely 2.60 mm, for all the pore structure parameters. This determination method can be used for the meso-scale pore structure analysis of grain soils such as sand soil and silty soil.
引文
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[14]王媛,冯迪,陈尚星,等.基于分维数的土体裂隙表征单元体估算[J].岩土力学,2013,34(10):2774-2780.WANG Yuan,FENG Di,CHEN Shang-xing,et al.Estimation of cracked soil’s representative elementary volume based on fractal dimension[J].Rock and Soil Mechanics,2013,34(10):2774-2780.
[15]朱建群,孔令伟,高文华,等.南京砂的稳态特征研究[J].岩土工程学报,2012,34(5):931-935.ZHU Jian-qun,KONG Ling-wei,GAO Wen-hua,et al.Steady-state properties of Nanjing sand[J].Chinese Journal of Geotechnical Engineering,2012,34(5):931-935.
[16]朱逢斌,陈甦,孙雷江,等.自制砂雨装置填砂装样质量分析[J].地下空间与工程学报,2013,9(增刊2):2076-2092.ZHU Feng-bin,CHEN Su,SUN Lei-jiang,et al.Quality analysis of sand filling by the self-made pluviation device[J].Chinese Journal of Underground Space and Engineering,2013,9(Suppl.2):2076-2092.
[17]马礼敦,杨福家.同步辐射应用概论[M].上海:复旦大学出版社,2001.MA Li-dun,YANG Fu-jia.Introduction to synchrotron radiation applications[M].Shanghai:Fudan University Press,2001.
[18]SILIN D B,JIN G,PATZEK T W.Robust determination of the pore space morphology in sedimentary rocks[J].Journal of Petroleum Technology,2004,56(5):69-70.
[19]徐炎达.砂土的孔隙尺度成像与孔隙网络建模[D].南京:南京大学,2015.XU Yan-da.Sandy soil's pore scale imaging and pore network modeling[D].Nanjing:Nanjing University,2015.
[20]DONG H,BLUNT M J.Pore-network extraction from micro-computerized-tomography images[J].Physical Review E,2009,80(3):1-11.
[21]DONG H,TOUATI M,BLUNT M.Pore network modeling:analysis of pore size distribution of Arabian core samples[C]//15th SPE Middle East Oil&Gas Show and Conference.[S.l.]:[s.n.],2007.
[22]WILDENSCHILD D,SHEPPARD A P.X-ray imaging and analysis techniques for quantifying pore-scale structure and processes in subsurface porous medium systems[J].Advances in Water Resources,2013,51(1):217-246.
[23]王晓明,夏露,郑银河,等.基于三维裂隙连通率的裂隙岩体表征单元体研究[J].岩石力学与工程学报,2013,32(增刊2):3297-3302.WANG Xiao-ming,XIA Lu,ZHENG Yin-he,et al.Study of representative elementary volume for fractured rock mass based on three-dimensional fracture connectivity[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(Suppl.2):3297-3302.
[24]王晓明,郑银河.裂隙岩体表征单元体及尺寸效应研究进展[J].岩土力学,2015,36(12):3456-3464.WANG Xiao-ming,ZHENG Yin-he.Review of advances in investigation of representative elementary volume and scale effect of fractured rock masses[J].Rock and Soil Mechanics,2015,36(12):3456-3464.
[2]张先伟,孔令伟.利用扫描电镜、压汞法、氮气吸附法评价近海黏土孔隙特征[J].岩土力学,2013,34(增刊2):134-142.ZHANG Xian-wei,KONG Ling-wei.Study of pore characteristics of offshore clay by SEM and MIP and NAmethods[J].Rock and Soil Mechanics,2013,34(Suppl.2):134-142.
[3]高原.压汞法常见问题分析[C]//第七届全国颗粒测试学术会议、2008上海市颗粒学会年会论文集.上海:[出版者不详],2008.GAO Yuan.Common problems in MIP[C]//Proceedings of the Seventh National Conference on Particle Size Testing and 2008 Annual Conference of Shanghai Society of Particuology.Shanghai:[s.n.],2008.
[4]BLUNT M,BIJELJIC B,DONG H,et al.Pore-scale imaging and modeling[J].Advances in Water Resources,2013,51(1):197-216.
[5]张巍,梁小龙,唐心煜,等.显微CT扫描南京粉砂空间孔隙结构的精细化表征[J].岩土工程学报,2017,39(4):683-689.ZHANG Wei,LIANG Xiao-long,TANG Xin-yu,et al.Fine characterization of spatial pore structure of Nanjing silty sand using micro-CT[J].Chinese Journal of Geotechnical Engineering,2017,39(4):683-689.
[6]BEAR J.Dynamics of fluids in porous media[M].New York:American Elsevier,1972:16-21.
[7]周创兵,陈益峰,姜清辉.岩体表征单元体与岩体力学参数[J].岩土工程学报,2007,29(8):1135-1142.ZHOU Chuang-bing,CHEN Yi-feng,JIANG Qing-hui.Representative elementary volume and mechanical parameters of fractured rock masses[J].Chinese Journal of Geotechnical Engineering,2007,29(8):1135-1142.
[8]ESMAIELI K,HADJIGEORGIOU J,GRENON M.Estimating geometrical and mechanical REV based on synthetic rock mass models at Brunswick mine[J].International Journal of Rock Mechanics and Mining Sciences,2010,47(6):915-926.
[9]朱万成,张敏思,张洪训,等.节理岩体表征单元体尺寸确定的数值模拟[J].岩土工程学报,2013,35(6):1121-1127.ZHU Wan-cheng,ZHANG Min-si,ZHANG Hong-xun,et al.Numerical simulation for determining the size of representative element volume(REV)of jointed rock mass[J].Chinese Journal of Geotechnical Engineering,2013,35(6):1121-1127.
[10]吴顺川,高艳华,高永涛,等.等效节理岩体表征单元体研究[J].岩土工程学报,2014,43(6):1120-1126.WU Shun-chuan,GAO Yan-hua,GAO Yong-tao,et al.Research on representative elementary volume of equivalent joint rock mass[J].Chinese Journal of Geotechnical Engineering,2014,43(6):1120-1126.
[11]吴琼,唐辉明,王亮清,等.基于三维离散元仿真试验的复杂节理岩体力学参数尺寸效应及空间各向异性研究[J].岩石力学与工程学报,2014,33(12):2419-2432.WU Qiong,TANG Hui-ming,WANG Liang-qing,et al.Three-dimensional distinct element simulation of size effect and spatial anisotropy of mechanical parameters of jointed rock mass[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(12):2419-2432.
[12]邸元,康志江,代亚非,等.复杂多孔介质多重介质模型的表征单元体[J].工程力学,2015,32(12):33-39.DI Yuan,KANG Zhi-jiang,DAI Ya-fei,et al.Representative elementary volume of the multiple continuum model for complex porous media[J].Engineering Mechanics,2015,32(12):33-39.
[13]黄丹,李小青.基于离散裂隙网络的表征单元体研究[J].武汉大学学报(工学版),2016,49(5):750-755.HUANG Dan,LI Xiao-qing.Research on representative elementary volume based on discrete fracture network[J].Engineering Journal of Wuhan University,2016,49(5):750-755.
[14]王媛,冯迪,陈尚星,等.基于分维数的土体裂隙表征单元体估算[J].岩土力学,2013,34(10):2774-2780.WANG Yuan,FENG Di,CHEN Shang-xing,et al.Estimation of cracked soil’s representative elementary volume based on fractal dimension[J].Rock and Soil Mechanics,2013,34(10):2774-2780.
[15]朱建群,孔令伟,高文华,等.南京砂的稳态特征研究[J].岩土工程学报,2012,34(5):931-935.ZHU Jian-qun,KONG Ling-wei,GAO Wen-hua,et al.Steady-state properties of Nanjing sand[J].Chinese Journal of Geotechnical Engineering,2012,34(5):931-935.
[16]朱逢斌,陈甦,孙雷江,等.自制砂雨装置填砂装样质量分析[J].地下空间与工程学报,2013,9(增刊2):2076-2092.ZHU Feng-bin,CHEN Su,SUN Lei-jiang,et al.Quality analysis of sand filling by the self-made pluviation device[J].Chinese Journal of Underground Space and Engineering,2013,9(Suppl.2):2076-2092.
[17]马礼敦,杨福家.同步辐射应用概论[M].上海:复旦大学出版社,2001.MA Li-dun,YANG Fu-jia.Introduction to synchrotron radiation applications[M].Shanghai:Fudan University Press,2001.
[18]SILIN D B,JIN G,PATZEK T W.Robust determination of the pore space morphology in sedimentary rocks[J].Journal of Petroleum Technology,2004,56(5):69-70.
[19]徐炎达.砂土的孔隙尺度成像与孔隙网络建模[D].南京:南京大学,2015.XU Yan-da.Sandy soil's pore scale imaging and pore network modeling[D].Nanjing:Nanjing University,2015.
[20]DONG H,BLUNT M J.Pore-network extraction from micro-computerized-tomography images[J].Physical Review E,2009,80(3):1-11.
[21]DONG H,TOUATI M,BLUNT M.Pore network modeling:analysis of pore size distribution of Arabian core samples[C]//15th SPE Middle East Oil&Gas Show and Conference.[S.l.]:[s.n.],2007.
[22]WILDENSCHILD D,SHEPPARD A P.X-ray imaging and analysis techniques for quantifying pore-scale structure and processes in subsurface porous medium systems[J].Advances in Water Resources,2013,51(1):217-246.
[23]王晓明,夏露,郑银河,等.基于三维裂隙连通率的裂隙岩体表征单元体研究[J].岩石力学与工程学报,2013,32(增刊2):3297-3302.WANG Xiao-ming,XIA Lu,ZHENG Yin-he,et al.Study of representative elementary volume for fractured rock mass based on three-dimensional fracture connectivity[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(Suppl.2):3297-3302.
[24]王晓明,郑银河.裂隙岩体表征单元体及尺寸效应研究进展[J].岩土力学,2015,36(12):3456-3464.WANG Xiao-ming,ZHENG Yin-he.Review of advances in investigation of representative elementary volume and scale effect of fractured rock masses[J].Rock and Soil Mechanics,2015,36(12):3456-3464.