基于Micro-CT的牛粪-麦秸好氧堆肥细观结构尺寸效应与RVE分析

Size Effect and Representative Volume Element Analysis of Meso-structure in Dairy Manure-wheat Straw Aerobic Composting Based on Micro-CT

摘要:

代表性体积单元（Representative volume element, RVE）是量化非均质材料有效参数的基础，也是应用等效连续介质理论表征好氧堆肥细观行为的前提。本文采用微计算机断层扫描（Micro-CT）和9点立方体覆盖采样窗口法，测量牛粪-麦秸好氧堆肥原状堆体的多元结构特征（包括总孔隙率、连通孔隙率、封闭孔隙率、分形维数、比表面积和连接密度），形成基于统计的细观结构Micro-CT-RVE分析方法。结果表明，堆体结构特征在边长0~51.2 mm范围内存在显著尺寸效应，且效应响应程度会随特征变化。当判定结构特征统计稳定时变异系数为5%，样品尺寸51.2 mm×51.2 mm×51.2 mm可满足RVE技术要求。研究结果揭示了堆体结构细观异质性与宏观均匀性的关系，为好氧堆肥微环境互作机制多尺度研究提供了理论依据和技术支撑。

Abstract:

The representative volume element (RVE) served as the foundation for quantifying the effective parameters of heterogeneous materials which was a prerequisite for characterizing the mesoscale behavior of aerobic composting by using equivalent continuum theory. Micro-computed tomography (Micro-CT) and the nine-point cubic coverage sampling window method were employed to measure the multiple structural characteristics (such as total porosity, connected porosity, enclosed porosity, fractal dimension, specific surface area, and connection density) of undisturbed aerobic composting piles composed of cow manure and wheat straw. A statistical-based mesoscale structure analysis method using Micro-CT-RVE was developed. The results indicated that the structural characteristics of the piles exhibited significant size effects within a range of 0~51.2 mm in edge length, and the degree of response to this effect varied with the characteristics. When the structural characteristics were determined to be statistically stable, the coefficient of variation was 5%, and a sample size of 51.2 mm×51.2 mm×51.2 mm met the technical requirements for RVE. The findings revealed the correlation between mesoscale heterogeneity and macroscale uniformity of the pile structure, providing theoretical basis and technical support for the multi-scale studies on microenvironmental interaction mechanisms in aerobic composting.