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基于土壤导气率的燥红土孔隙结构及弯曲连通性研究
王卫华, 张志鹏
昆明理工大学现代农业工程学院
摘要:
土壤气体传输高度依赖土壤孔隙结构,导气率的获取简单、快速、高效,且对土壤结构破坏小,利用PL-300土壤空气传导性测量系统分别对不同含水率、不同容重条件下的原状土与扰动土进行导气率测量,展开针对土壤孔隙结构与弯曲连通性的讨论。结果表明:(1)原状土样本孔隙弯曲连通性随气相饱和度增加而增加的程度较扰动土样本显著,两者相对导气率与饱和度的关系曲线变化走势差异不大,表明即便饱和度一样的条件下,孔隙弯曲连通程度仍然不同;(2)原状土导气率依赖于大孔隙的存在,扰动土导气率不仅依赖于孔隙连通的程度,还取决于孔隙弯曲程度。基于土壤导气率对土壤孔隙结构及弯曲连通性的讨论,在建立气体传输模型时应考虑孔隙尺寸分布对导气率的影响,就原状土与扰动土不同的弯曲连通系数加以区分与讨论,为进一步揭示土壤气体传输的内在机制提供参考。
关键词:  孔隙结构  孔隙连通性  土壤导气率  燥红土
DOI:10.11766/trxb201707070161
分类号:
基金项目:国家自然科学基金项目(51409136)、昆明理工大学自然科学研究基金项目(KKSY201423023)、昆明理工大学学生课外学术创新基金(2015BA130)
Discussion on the soil pore structure and pore tortuosity-connectivity based on soil air permeability
WANG Weihua, ZHANG Zhipeng
Faculty of Modern Agricultural Engineering,
Abstract:
【Objective】The characteristics of soil hydraulic conductivity are used to construct the geometric model of pore parameters, but the variation of hydraulic parameters in field is usually very large and the measurement efficiency is low. Soil air transmission is highly dependent on soil pore structure and acquisition of the air permeability is simple, fast, and efficient, and little damage to soil structure.Using soil air permeability rate to analyze soil structure and pore geometry distribution is becoming the focus of attention.【Method】We use soil air permeability measurement instrument (PL-300) to get the air permeability, and use the centrifuge to get the soil water characteristic curve.We measured the air permeability of undisturbed and disturbed soils under different water contents and different soil bulks, through the two relative air permeability curve fitting bending pore connectivity factor, we discussed the pore structure and pore tortuosity-connectivity.【Result】The results showed that: 1) Pore tortuosity-connectivity increased with air phase saturation increasing,and the increase degree of undisturbed soil is more significant than disturbed soil. When the air saturation is 18%, 32%, 60% and 86% , the relative permeability of the disturbed soil is respectively 50.77%, 51.65%, 50.31%, and 51.02% of the undisturbed soil. The trend curves of relative air permeability and saturation, both of undisturbed and disturbed soil, were basic same, but not coincident. Which means that the degrees of pore tortuosity-connectivity is different, even if the saturation of undisturbed soil and disturbed soil are same. 2) The air permeability of undisturbed soil depended on the existence of macroporosity, while the air permeability of disturbed soil not only depended on the degree of pore connectivity, but also depended on pore tortuosity-connectivity.【Conclusion】Based on the discussion which soil air permeability create the change of soil pore structure make for pore geometry feature differences, in the soil air transmission and pore structure of the related research and the process of application in mathematical model, in addition to the analysis of soil physical basic parameters, should be taken into account the influence of pore size distribution on air permeability under the condition of high moisture content, distinguishing and discussing undisturbed and disturbed soil different bending connectivity factor, in order to further reveal the internal mechanism of soil air transmission to provide the reference.
Key words:  soil pore structure  pore tortuosity-connectivity  soil air permeability  red soil