摘要
三峡库区库水位周期性升降使库岸消落带土体经历着干湿循环作用,导致土体的孔隙结构和土水特性发生变化,影响库岸岩土体渗流和应力进程。以三峡库区八字门滑坡消落带土体为研究对象,开展了不同干湿循环周期条件下的土水特征曲线测试试验,通过建立考虑孔隙大小和分布影响的土水特征曲线模型,结合扫描电镜试验对消落带土体孔隙微细观结构和土水特性的变化规律进行了分析。结果表明:(1)在干湿循环作用下消落带土体土水特征曲线整体向左偏移,3次干湿循环后,干湿循环作用对土水特性的影响逐渐减弱;(2)所提出的土水特征曲线模型对试验结果拟合效果较好,模型参数物理意义明确,能较好地适用于分析土体非饱和土水特性变化的孔隙结构微细观机制;(3)随着干湿循环次数的增加,土体孔隙体积增加,最大等效孔隙半径增大,分形维数降低,说明干湿循环作用可以有效增大土体孔隙尺寸,降低孔隙分布的复杂程度,导致土体持水能力降低;(4)电镜扫描试验进一步说明消落带原状土经历干湿循环作用后,土体内部大孔隙和微裂隙增加,微观结构逐渐松散,是导致最大等效孔隙半径增大和分形维数降低的主要原因。
The fluctuation of water levels in the Three Gorges Reservoir causes a cyclical wet-dry environment for the soil in the hydro-fluctuation belt,leading to alterations in pore structure and soil-water characteristics.Consequently,the seepage and mechanical processes of the reservoir bank are influenced.This study conducted experimental tests on the soil-water characteristics of the hydro-fluctuation belt soil in the Bazimen landslide area of the Three Gorges Reservoir.These tests examined the effect of varying dry-wet cycles on the soil-water characteristic curve(SWCC).A novel SWCC model was proposed to analyze the changes in pore structure under dry-wet cycles and its correlation with SWCC,taking into account the influence of pore size magnitude and distribution.The alterations in microstructure were validated through a comparison of the results obtained from scanning electron microscopy(SEM).The following findings are obtained:(1)The SWCC of the soil from the hydro-fluctuation belt tends to shift towards the left as a result of dry-wet cycles.As the cycle period increases,the impact of dry-wet cycles on SWCC gradually diminishes.(2)The proposed model encompasses several parameters with clear physical meaning,and the SWCC results predicted from the proposed model matches well with the experimental data.The correspondence illustrates that the proposed model is capable of describing the SWCC behavior of unsaturated soil in relation to variations in pore size and distribution resulting from dry-wet cycles.(3)The dry-wet cycles can significantly increase the size of soil pores and simplify the complexity of pore size distribution.As the number of dry-wet cycles increases,the maximum equivalent pore radius increases while the fractal dimension decreases,leading to a decrease in water holding capacity.(4)The SEM test provides additional evidence that the soil experiences pore enlargement and an increase in micro-cracks after undergoing dry-wet cycles,resulting in a gradual loosening of the microstructure.This phenomenon is likely the primary cause for the observed increase in maximum equivalent pore radius and decrease in fractal dimension.
作者
李彪
刘健
刘畅
童富果
田斌
杨佳璐
LI Biao;LIU Jian;LIU Chang;TONG Fuguo;TIAN Bin;YANG Jialu(Hubei Key Laboratory of Hydropower Engineering Construction and Management(China Three Gorges University),Yichang 443002,China;China Three Gorges University College of Hydraulic and Environmental Engineering,Yichang 443002,China)
出处
《工程地质学报》
北大核心
2025年第5期1969-1977,共9页
Journal of Engineering Geology
基金
湖北省自然科学基金一般面上项目(资助号:2022CFB337)
湖北省自然科学基金一般青年项目(资助号:2023AFB036)
国家自然科学基金重点项目(资助号:51939004)。
关键词
土水特征曲线
干湿循环
基质吸力
孔径分布
三峡库区
Soil-water characteristic curve
Dry-wet cycles
Suction
Pore size distribution
Three Gorges Reservoir area
作者简介
第一作者:李彪(1990-),男,博士,讲师,主要从事库岸边坡工程与灾害防治方面的研究.E-mail:libiao_1717@163.com;通讯作者:刘畅(1989-),女,博士,讲师,主要从事岩土工程多相流及多场耦合等方面的研究.E-mail:lc_ctgu@163.com。
