钙质砂颗粒内孔隙三维表征
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摘要
南海钙质砂颗粒形状复杂,颗粒棱角突出且面孔隙与内孔隙结构发达.为了准确表征钙质砂内孔隙三维形态,本文借助高精度X射线μCT扫描技术,得到钙质砂颗粒高精度断层图像.通过对原始CT扫描断层图像切割、除噪、二值化等一系列操作,重构得到钙质砂颗粒三维图像.由于钙质砂颗粒外形不规则,因此直接提取其内部孔隙较为困难,本文通过对钙质砂颗粒的三维图像进行三维闭合运算等一系列算法的处理,较好地重构了钙质砂内部的三维孔隙.根据块状钙质砂颗粒的外表特征、内孔隙孔隙率的大小、孔径分布曲线形状以及分形维数的大小,可以大致将块状钙质砂颗粒分为两种类型.第1种类型块状钙质砂颗粒外表存在较多沟壑且内孔隙较为发达,第2种类型块状钙质砂颗粒内孔隙较不发达且连通性较低.两种类型块状钙质砂颗粒内孔隙的孔隙率与孔径分布曲线存在明显差异.同时研究发现,钙质砂颗粒内孔隙较好地符合三维分形特征,且分形维数的大小与孔隙率大小成正相关关系.为了深入地研究钙质砂颗粒内部孔隙的连通性,本文通过计算其距离图获得颗粒内孔隙的空间网络模型,对其分析得出,钙质砂颗粒网络模型的配位数分布大体趋势相同,由于两种钙质砂颗粒内孔隙形态的差异,配位数的分布也略有差异.
The shape of the calcareous sand particles found near the South China Sea is complex. The edges of these particles are prominent,and the surface pore and inner pore structures are developed. In order to accurately characterize the three-dimensional(3D) shape of the pores in calcareous sand particles,high-precision tomographic images of the calcareous sand particles were obtained using a high-precision X-ray μCT scanning technique. The 3D image of the calcareous sand particles was reconstructed through cutting,denoising,binarization,and other operations on the original CT scan image. As the shape of calcareous sand particles is irregular,it is difficult to extract the internal pores directly. In this paper,a series of algorithms,such as 3D closing algorithm,were used to reconstruct the interior structure of calcareous sand. According to the appearance characteristics of the calcareous sand particles,porosity of the inner pores,shape of the pore size distribution curve,and fractal dimension,calcareous sand particles can be roughly classified into two types. The first type of calcareous sand particles has more gullies on the surface;its inner pores are more developed. The inner pores of the second type of calcareous sand particles are less developed and have lower connectivity. The porosity and pore size distribution curves of the two types of calcareous sand particles are significantly different. Furthermore,it is found that pores in the calcareous sand particles conform to the 3D fractal characteristics,and the value of the fractal dimension is positively correlated with the value of porosity. In order to deeply study the connectivity of inner pores in calcareous sand particles,the space network model of the inner pores was obtained by calculating the distance map. It can be concluded that all the distribution of the coordination number of the calcareous sand particle network model has the same general trend. Additionally,owing to the difference in pore morphology between the two types of calcareous sand particles,the distribution of their coordination numbers is slightly different.
The shape of the calcareous sand particles found near the South China Sea is complex. The edges of these particles are prominent,and the surface pore and inner pore structures are developed. In order to accurately characterize the three-dimensional(3D) shape of the pores in calcareous sand particles,high-precision tomographic images of the calcareous sand particles were obtained using a high-precision X-ray μCT scanning technique. The 3D image of the calcareous sand particles was reconstructed through cutting,denoising,binarization,and other operations on the original CT scan image. As the shape of calcareous sand particles is irregular,it is difficult to extract the internal pores directly. In this paper,a series of algorithms,such as 3D closing algorithm,were used to reconstruct the interior structure of calcareous sand. According to the appearance characteristics of the calcareous sand particles,porosity of the inner pores,shape of the pore size distribution curve,and fractal dimension,calcareous sand particles can be roughly classified into two types. The first type of calcareous sand particles has more gullies on the surface;its inner pores are more developed. The inner pores of the second type of calcareous sand particles are less developed and have lower connectivity. The porosity and pore size distribution curves of the two types of calcareous sand particles are significantly different. Furthermore,it is found that pores in the calcareous sand particles conform to the 3D fractal characteristics,and the value of the fractal dimension is positively correlated with the value of porosity. In order to deeply study the connectivity of inner pores in calcareous sand particles,the space network model of the inner pores was obtained by calculating the distance map. It can be concluded that all the distribution of the coordination number of the calcareous sand particle network model has the same general trend. Additionally,owing to the difference in pore morphology between the two types of calcareous sand particles,the distribution of their coordination numbers is slightly different.
引文
[1]吴京平,褚瑶,楼志刚.颗粒破碎对钙质砂变形及强度特性的影响[J].岩土工程学报,1997,19(5):51-57.Wu Jingping,Chu Yao,Lou Zhigang.Influence of particle breakage on deformation and strengt properties of calcareous soils[J].Chinese Journal of Geotechnical Engineering,1997,19(5):51-57(in Chinese).
[2]孙吉主,黄明利,汪稔.内孔隙与各向异性对钙质砂液化特性的影响[J].岩土力学,2002,23(2):166-169.Sun Jizhu,Huang Mingli,Wang Ren.Influence of inner pore and anisotropy on liquefaction characteristics of calcareous sands[J].Rock and Soil Mechanics,2002,23(2):166-169(in Chinese).
[3]Alshibli K A,Druckrey A M,Al-Raoush R I,et al.Quantifying morphology of sands using 3D imaging[J].Journal of Materials in Civil Engineering,2014,27(10):04014275.
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[5]Wei D,Wang J,Nie J,et al.Generation of realistic sand particles with fractal nature using an improved spherical harmonic analysis[J].Computers and Geotechnics,2018,104:1-12.
[6]Katz A J,Thompson A H.Fractal sandstone pores:Implications for conductivity and pore formation[J].Physical Review Letters,1985,54(12):1325-1328.
[7]Yu B,Liu W.Fractal analysis of permeabilities for porous media[J].AIChE Journal,2004,50(1):46-57.
[8]Lindquist W B,Lee S M,Coker D A,et al.Medial axis analysis of void structure in three dimensional tomographic images of porous media[J].Journal of Geophysical Research:Solid Earth,1996,101(B4):8297-8310.
[9]Baldwin C A,Sederman A J,Mantle M D,et al.Determination and characterization of the structure of a pore space from 3D volume images[J].Journal of Colloid and Interface Science,1996,181(1):79-92.
[10]Silin D B,Jin G,Patzek T W.Robust determination of the pore space morphology in sedimentary rocks[C]//SPE Annual Technical Conference and Exhibition.Society of Petroleum Engineers,Denver,Colorado,USA,2003.
[11]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,2013,51:217-246.
[12]朱长歧,陈海洋,孟庆山,等.钙质砂颗粒内孔隙的结构特征分析[J].岩土力学,2014,35(7):1831-1836.Zhu Changqi,Chen Haiyang,Meng Qingshan,et al.Microscopic characterization of intra-pore structures of calcareous sands[J].Rock and Soil Mechanics,2014,35(7):1831-1836(in Chinese).
[13]蒋明镜,吴迪,曹培,等.基于SEM图片的钙质砂连通孔隙分析[J].岩土工程学报,2017,39(增1):1-5.Jiang Mingjing,Wu Di,Cao Pei,et al.Connected inner pore analysis of calcareous sands using SEM[J].Chinese Journal of Geotechnical Engineering,2017,39(Suppl.1):1-5(in Chinese).
[14]吕海波,汪稔.钙质土破碎原因的细观分析初探[J].岩石力学与工程学报,2001,20(增1):890-892.LüHaibo,Wang Ren.Preliminary mesoscopic analysis on factors of breakage in calcareous soil[J].Chinese Journal of Rock Mechanics and Engineering,2001,20(Suppl.1):890-982(in Chinese).
[15]陈海洋.钙质砂的内孔隙研究[D].武汉:中国科学院研究生院武汉岩土力学研究所,2005.Chen Haiyang.Study of the Inner Pore in Calcareous Sand[D].Wuhan:Institute of Rock and Soil Mechanics,Chinese Academy of Science,2005(in Chinese).
[16]Otsu N.A threshold selection method from gray-level histograms[J].IEEE Transactions on Systems,Man,and Cybernetics,1979,9(1):62-66.
[17]Lange D A,Jennings H M,Shah S P.Image analysis techniques for characterization of pore structure of cement-based materials[J].Cement and Concrete Research,1994,24(5):841-853.
[18]Diamond S,Leeman M E.Pore size distributions in hardened cement paste by image analysis[C]//Mater Res Soc Symp Proc.Boston,USA,1995,370:217-226.
[19]Münch B,Holzer L.Contradicting geometrical concepts in pore size analysis attained with electron microscopy and mercury intrusion[J].Journal of the American Ceramic Society,2008,91(12):4059-4067.
[20]Dong H,Gao P,Ye G.Characterization and comparison of capillary pore structures of digital cement pastes[J].Materials and Structures,2017,50(2):154.
[21]Falconer K.Fractal Geometry:Mathematical Foundations and Applications[M].New York:John Wiley&Sons,1990.
[2]孙吉主,黄明利,汪稔.内孔隙与各向异性对钙质砂液化特性的影响[J].岩土力学,2002,23(2):166-169.Sun Jizhu,Huang Mingli,Wang Ren.Influence of inner pore and anisotropy on liquefaction characteristics of calcareous sands[J].Rock and Soil Mechanics,2002,23(2):166-169(in Chinese).
[3]Alshibli K A,Druckrey A M,Al-Raoush R I,et al.Quantifying morphology of sands using 3D imaging[J].Journal of Materials in Civil Engineering,2014,27(10):04014275.
[4]Zhou B,Wang J,Wang H.Three-dimensional sphericity,roundness and fractal dimension of sand particles[J].Géotechnique,2018,68(1):18-30.
[5]Wei D,Wang J,Nie J,et al.Generation of realistic sand particles with fractal nature using an improved spherical harmonic analysis[J].Computers and Geotechnics,2018,104:1-12.
[6]Katz A J,Thompson A H.Fractal sandstone pores:Implications for conductivity and pore formation[J].Physical Review Letters,1985,54(12):1325-1328.
[7]Yu B,Liu W.Fractal analysis of permeabilities for porous media[J].AIChE Journal,2004,50(1):46-57.
[8]Lindquist W B,Lee S M,Coker D A,et al.Medial axis analysis of void structure in three dimensional tomographic images of porous media[J].Journal of Geophysical Research:Solid Earth,1996,101(B4):8297-8310.
[9]Baldwin C A,Sederman A J,Mantle M D,et al.Determination and characterization of the structure of a pore space from 3D volume images[J].Journal of Colloid and Interface Science,1996,181(1):79-92.
[10]Silin D B,Jin G,Patzek T W.Robust determination of the pore space morphology in sedimentary rocks[C]//SPE Annual Technical Conference and Exhibition.Society of Petroleum Engineers,Denver,Colorado,USA,2003.
[11]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,2013,51:217-246.
[12]朱长歧,陈海洋,孟庆山,等.钙质砂颗粒内孔隙的结构特征分析[J].岩土力学,2014,35(7):1831-1836.Zhu Changqi,Chen Haiyang,Meng Qingshan,et al.Microscopic characterization of intra-pore structures of calcareous sands[J].Rock and Soil Mechanics,2014,35(7):1831-1836(in Chinese).
[13]蒋明镜,吴迪,曹培,等.基于SEM图片的钙质砂连通孔隙分析[J].岩土工程学报,2017,39(增1):1-5.Jiang Mingjing,Wu Di,Cao Pei,et al.Connected inner pore analysis of calcareous sands using SEM[J].Chinese Journal of Geotechnical Engineering,2017,39(Suppl.1):1-5(in Chinese).
[14]吕海波,汪稔.钙质土破碎原因的细观分析初探[J].岩石力学与工程学报,2001,20(增1):890-892.LüHaibo,Wang Ren.Preliminary mesoscopic analysis on factors of breakage in calcareous soil[J].Chinese Journal of Rock Mechanics and Engineering,2001,20(Suppl.1):890-982(in Chinese).
[15]陈海洋.钙质砂的内孔隙研究[D].武汉:中国科学院研究生院武汉岩土力学研究所,2005.Chen Haiyang.Study of the Inner Pore in Calcareous Sand[D].Wuhan:Institute of Rock and Soil Mechanics,Chinese Academy of Science,2005(in Chinese).
[16]Otsu N.A threshold selection method from gray-level histograms[J].IEEE Transactions on Systems,Man,and Cybernetics,1979,9(1):62-66.
[17]Lange D A,Jennings H M,Shah S P.Image analysis techniques for characterization of pore structure of cement-based materials[J].Cement and Concrete Research,1994,24(5):841-853.
[18]Diamond S,Leeman M E.Pore size distributions in hardened cement paste by image analysis[C]//Mater Res Soc Symp Proc.Boston,USA,1995,370:217-226.
[19]Münch B,Holzer L.Contradicting geometrical concepts in pore size analysis attained with electron microscopy and mercury intrusion[J].Journal of the American Ceramic Society,2008,91(12):4059-4067.
[20]Dong H,Gao P,Ye G.Characterization and comparison of capillary pore structures of digital cement pastes[J].Materials and Structures,2017,50(2):154.
[21]Falconer K.Fractal Geometry:Mathematical Foundations and Applications[M].New York:John Wiley&Sons,1990.
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