农业工程学报2026，Vol.42Issue(5)：158-166,9.DOI:10.11975/j.issn.1002-6819.202506108
初始裂隙扰动下紫色土的土水特征曲线
Soil-water characteristic curve of sandy viscous purple soil under initial fissure disturbance
摘要
Abstract
Purple soil is often characterized by a loose structure and high erodibility,particularly prone to desiccation cracks under the alternating action of the rainfall and evaporation.These cracks can significantly damage the integrity of the soil structure and further degrade its water-holding capacity.This study aims to systematically clarify the influence of the initial cracks on the water-holding capacity of the purple soil.The undisturbed ring knife samples were prepared with the initial crack parameters,including the crack ratio,crack length,average crack width,and crack number.The soil-water characteristic curve(SWCC)of each sample was obtained using the axis translation.The Fredlund-Xing model was adopted to conduct fitting analysis on the measured SWCC data.Meanwhile,the grey correlation analysis was employed to explore the influence of the various crack parameters on the characteristic parameters of the SWCC and the fitting parameters of the Fredlund-Xing model.Additionally,the low-field nuclear magnetic resonance(NMR)scanning tests,including the nuclear magnetic resonance T2 spectra analysis and pore throat distribution analysis,were carried out to verify the correlation between soil pore distribution and crack development.The results indicated that the influence of the initial cracks on the water-holding characteristics of the purple soil was concentrated mainly in the low suction section of the SWCC,indicating the rapid dehydration that was accompanied by the"plateau period".In contrast,the initial cracks had a minimal impact on the transition and residual section of the SWCC,where the water-holding characteristics remained relatively stable.Further analysis showed that the air-entry value of the soil was inversely proportional to the crack ratio and dehumidification rate.The Fredlund-Xing model sand showed an excellent fitting performance for the SWCC of the purple soil with the initial cracks,particularly with the determination coefficient generally higher than 0.85.The parameter,α,which was closely related to the air-entry value,was inversely proportional to the crack ratio and dehumidification rate.While the parameters n and c showed no significant linear correlation with any crack parameters.The grey correlation analysis revealed that the crack ratio was the primary dominant influencing factor on the water-holding capacity of the purple soil(correlation degree＞0.67),followed by the average crack width,whereas the crack number shared the weakest correlation with the water-holding capacity.The initial cracks also destroyed the internal structure of the soil.Thus,a dual-pore system was formed with the interconnected crack space and intact non-cracked soil matrix.The proportion of the large pores was dominated by the macro-cracks,while there was a relative decrease in the proportion of the medium and small pores that were controlled by the soil matrix.The preferential water flow effect of the crack system was reduced in the soil air-entry value at the low suction stage.The"plateau period"also occurred in the SWCC.The NMR scanning tests confirmed that there was a close correlation between pore distribution and crack development:The nuclear magnetic resonance T2 spectra and pore throat distribution verified the negative effect of the cracks on the soil pore distribution.A multi-scale verification on the SWCC was integrated with the macro water-holding,micro pore structure,and model fitting parameters under crack disturbance.The dominant role of the crack network was clarified as a preferential water flow path to regulate the soil hydraulic behavior.The influence mechanism of the initial cracks on the water-holding of the purple soil can provide a solid theoretical basis and key parameter support for soil and water conservation,soil improvement,and accurate thresholds of the landslide disaster early warning in purple soil distribution areas.关键词
紫色土/土-水特征曲线/初始裂隙/孔隙分布/NMRKey words
purple soil/soil-water characteristic curve/initial fissure/pore distribution/NMR分类
农业科技引用本文复制引用
向超,汪时机,曹俊嘉,黎桉君,覃永富,梅立奎,田如梦..初始裂隙扰动下紫色土的土水特征曲线[J].农业工程学报,2026,42(5):158-166,9.基金项目
国家自然科学基金项目(11972311) （11972311）
重庆英才计划"包干制"项目(cstc2024ycjh-bgzxm0054) （cstc2024ycjh-bgzxm0054）
西南大学创新研究2035先导计划项目(SWU-XDPY22003) （SWU-XDPY22003）
