Investigating encroachment behaviour of pore water on pore structure of unsaturated loess using continuous NMR technique

Abstract

To study the influence of the evolution of pore structure and pore fluid state on the loading effect of unsaturated loess, a series of oedometer tests were carried out on intact and remoulded loess, supplemented by low-field nuclear magnetic resonance (NMR) tests at different consolidation stages of the same specimens for the first time. The results show that the deformation of intact loess lags behind that of remoulded loess during mechanical wetting. The pore water gradually encroaches on the pore structure, which increases the debonding effect of soil and the behaviour of loess gradually converges to that of saturated loess. Under the same vertical pressure, unsaturated loess maintains a higher void ratio than saturated. The decrease in the relaxation time span predicts the compression of the pore structure and the gradual encroachment of water. Deformation caused by consolidation enhances the water retention performance of unsaturated loess. The results provide guidance for understanding the evolution of micropore fabrics in the compaction process of loess.