摘要
非饱和土的渗透系数作为研究非饱和土中水分运移的重要参数,直接测量方法原理简明但试样尺寸较大,耗时较长;土-水特征曲线(SWCC)间接预测方法由于需要获取土-水特征曲线,同样较为耗时,工作量较大。为此,结合核磁共振(NMR)理论与渗流理论提出了不同孔径孔隙通道渗透系数与弛豫时间的关系,通过对不同大小孔隙通道渗透系数进行累加,提出了基于核磁共振的饱和/非饱和土渗透系数预测模型和快速预测方法。为验证模型的合理性,以湖南黏土为研究对象,进行了不同初始孔隙比试样脱湿、吸湿过程以及饱和状态下的95次核磁共振试验,获取相应的NMR曲线,采用瞬时剖面法获取不同初始孔隙比试样非饱和相对渗透系数,并与该模型预测值对比。研究发现:利用脱湿、吸湿过程不同含水率下NMR曲线以及饱和状态的NMR曲线均具有较好的预测效果,但基于饱和状态下试样的NMR曲线预测效果相对最好,测量成本和耗时也最小,因此建议采用饱和状态试样NMR曲线直接预测非饱和相对渗透系数。
The permeability coefficient of unsaturated soils is a particularly important parameter to study the moisture migration in unsaturated soils.The direct measurement methods have a straightforward principle,but they require larger sample sizes and longer testing time.The indirect prediction methods based on the soil-water characteristic curve(SWCC)also demand significant time and effort due to the necessity of acquiring the SWCC data.Thus,this paper combines the nuclear magnetic resonance(NMR)theory with the seepage theory to establish the relationship between the permeability coefficient and the relaxation time of pore channels with different pore sizes.Through the accumulation of permeability coefficients of different pore channels,an NMR-based prediction model and a rapid prediction method for the permeability coefficients of saturated/unsaturated soils are proposed.To verify the rationality of the model,taking the Hunan clay as the research object,95 times NMR tests are conducted on desorption,absorption and saturated samples with different initial void ratios to obtain the corresponding NMR curves.The unsaturated relative permeability of samples with different void ratios is gained by the instantaneous profile method and compared with the predicted value of the model.The study shows that the NMR curves of desorption,absorption and saturated samples all possess good prediction effecst,while the saturated state NMR curves have the best prediction accuracy with the lowest measurement cost and the shortest time consumption.Therefore,it is suggested to use the NMR curves of saturated samples to predict the unsaturated relative permeability coefficient directly.
作者
陶高梁
彭寅杰
陈银
肖衡林
罗晨晨
钟楚珩
雷达
TAO Gaoliang;PENG Yinjie;CHEN Yin;XIAO Henglin;LUO Chenchen;ZHONG Chuheng;LEI Da(Key Laboratory of Intelligent Health Perception and Ecological Restoration of Rivers and Lakes,Ministry of Education,Hubei University of Technology,Wuhan 430068,China;School of Intelligent Construction,Wuchang University of Technology,Wuhan 430223,China)
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2024年第3期470-479,共10页
Chinese Journal of Geotechnical Engineering
基金
国家自然科学基金面上项目(51978249,52078195)
国家自然科学基金联合基金项目(U22A20232)。
关键词
核磁共振
饱和/非饱和渗透系数
孔隙通道
弛豫时间
nuclear magnetic resonance
saturated/unsaturated permeability coefficient
pore channel
relaxation time
