Abstract: The soil-water characteristic curve (SWCC) is a curve that describing the relationship between the soil moisture content and the matrix suction, and it is an important constitutive relationship in the unsaturated soil mechanics. The traditional testing method of gradually the applying suction and obtaining the moisture content in equilibrium is usually both time and labor consuming. Based on the recently developed new method of using nuclear magnetic resonance (NMR) technique, this paper presents a method of rapid determining the SWCC of compacted loess and the results are compared with the measured data. The results show that the soil-water properties of compacted Yan’an loess are greatly affected by the initial moisture content and dry density. Both methods have different influence mechanisms. The rapid determination method has a better predictive result for the soil-water characteristic relationship curve of the compacted loess with higher dry density, while the predictive result of soil-water characteristic relationship for the lower dry density soil samples is slightly worse. The main reason is that the higher the compaction density, the closer the measured porous distribution is to the unimodal distribution, and the more accurate prediction results. For the prediction of soil-water characteristic curve with obvious bimodal porous size distribution, the rapid method needs to be further investigated.

Key words: loess, soil-water characteristics curve, nuclear magnetic resonance technique, dry density, water content