基于最大球算法定量表征土体空间孔隙网络

孔隙网络控制着土体渗流、排水固结与基质吸力等重要工程性质。本文介绍了多孔介质孔隙网络最大球建模基本原理与算法。以显微CT扫描振捣干法生成的南京粉砂试样为例,采用最大球算法建立了试样三维重构模型表征单元体(REV)的空间孔隙网络球棍模型,计算得到了样品REV尺度的孔隙网络参数,统计发现,孔隙半径、喉道半径、孔隙配位数、孔隙截面形状因子、喉道截面形状因子与喉道长度等孔隙参数均近似服从正态分布,孔隙体积近似服从衰减型指数分布。孔隙与喉道半径分别分布在100μm与65μm以内,两者数学期望分别为40. 0μm与18. 0μm;配位数分布在25以内,数学期望为5. 1;孔隙与喉道截面形状因子分别分布在0. 01~0. 04与0. 01~0. 05的区间内,两者数学期望分别为0. 019与0. 033;喉道长度分布在100~800μm以内,数学期望为292. 22μm。同时发现,样品中体积小于1. 5×10^7μm^3的小孔隙数量超过90%。本方法可应用于土体细观孔隙结构的定量表征。

QUANTITATIVE CHARACTERIZATION OF SPATIAL PORE NETWORK OF SOILS BASED ON MAXIMAL-BALLS ALGORITHM

Pore network controls important engineering properties of the soil such as seepage,drainage consolidation and matrix suction. This article introduces the basic principle and algorithm of the maximal ball algorithm used in establishing the pore network model of the soil space. Taking the Nanjing silty sand specimen fabricated by vibrating-dry method and scanned by micro-CT as an example,we use the maximal ball algorithm to extract the spatial pore network ball-stick model for Representative Element Volume(REV)in the three-dimensional reconstruction model of the specimen,and calculates the pore network parameters at REV scale. Statistical results shows that the pore parameters such as pore radius,throat radius,pore coordination number,area shape factor of pore,area shape factor of throat and throat length approximately obey the normal distribution,the pore volume approximately obeys the attenuation exponential distribution. The pore radius and throat radius distributes within 100 μm and 65 μm respectively,and their mathematical expectations are 40 μm and 18 μm; the pore coordination number distributes within 25 and the mathematical expectation is 5.1; the area shape factor of pore and area shape factor of throat distributes in the range of 0.01~0.04 and 0.01~0.05 respectively,and their mathematical expectations are 0.019 and 0.033; the throat length distributes in the range of 100~800 μm and the mathematical expectation is 292.22 μm. Meanwhile,we find that the number of small pore with volume less than1.5×107 μm3 is more than 90%. This method can be used to the quantitative characterization of micro pore structure of soil.