Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering, Guilin University of Technology, Guilin 541004, PR China.
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China.
Magn Reson Imaging. 2024 Jan;105:1-9. doi: 10.1016/j.mri.2023.09.008. Epub 2023 Sep 26.
Measuring hydraulic conductivity by instantaneous profile method needs to detect the pore water content of soil at different positions, but most of the detecting methods will disturb the soil sample. In the study, the axial slice scanning of soil samples was carried out by using static filed gradient multi-slice Carr-Purcell-Meiboom-Gill (SFG-MSCPMG) sequence of nuclear magnetic resonance (NMR) technology, which can nondestructively determine water content and distribution at different positions of soil column. In this experiment, three clays were used to illustrate the relationship between NMR test results and oven drying results of water content. The results show that there is a good linear relationship between the NMR signal and water content. Combining mercury intrusion porosimetry (MIP) data, the transverse surface relaxivity parameters (ρ) of clays are obtained. With ρ = 41.90 μm/s the T distribution curve of pore water in the ordinary clay can be converted into the pore water distribution curve, which is in good agreement with that obtained with MIP. Nevertheless, it is found that the T distribution curve of pore water in expansive clay obtained with NMR technique is more suitable for analyzing the average pore water distribution because of the fast exchange of pore water between the interlayers, intra-aggregates and inter-aggregates in expansive clay.
采用瞬时剖面法测量水力传导度需要检测土壤中不同位置的孔隙水含量，但大多数检测方法都会对土壤样品造成干扰。在本研究中，采用核磁共振（NMR）技术中的静态磁场梯度多切片 Carr-Purcell-Meiboom-Gill（SFG-MSCPMG）序列对土柱进行轴向切片扫描，可无损测定土柱不同位置的含水量及其分布。本实验采用三种粘土来说明 NMR 测试结果与烘干法测含水量之间的关系。结果表明，NMR 信号与含水量之间存在良好的线性关系。结合压汞法（MIP）数据，得到粘土的横向表面弛豫率参数（ρ）。利用 ρ=41.90μm/s 可以将普通粘土中孔隙水的 T 分布曲线转换为孔隙水分布曲线，与 MIP 得到的结果吻合较好。然而，研究发现，由于膨胀土的层间、团聚体内和团聚体间的孔隙水快速交换，NMR 技术得到的膨胀土中孔隙水的 T 分布曲线更适合分析平均孔隙水分布。
