Experimental study on the micromechanism of salt influence on the permeability of remolded loess

The construction of reservoirs by "gully land consolidation" leads to soil salinization, and the permeability of saline soil is an important factor affecting engineering design and construction safety. Therefore, it is important to clarify the remolded loess permeability under different salt content and type conditions. In this study, a series of indoor variable head permeability tests was carried out to investigate the variation of permeability coefficient of remolded loess with salt content by preparing sodium and calcium salt remolded loess specimens with different salt contents. The results indicated that with the increase of salt content, the saturation permeability coefficient of remolded loess gradually decreases, and the two are negatively correlated. Moreover, the permeability coefficient of salt-containing remolded loess decreased to varying degrees compared with that of remolded loess without salt. Under the same salt content, the permeability coefficient of calcium-salt loess was smaller than that of sodium-salt loess. The variation of pore water fugacity and pore structure with salt content and type within the specimen was tested using nuclear magnetic resonance (NMR) techniques. When the salt content was below 2%, the permeability of remolded loess decreased rapidly with the increase of salt content, due to the changes in pore water occurrence state and pore structure. However, when the salt content exceeded 2%, the permeability of the remolded loess increased with the change of pore water occurrence state, while the permeability of the remolded loess decreased with the change of pore structure, and the change of pore structure had a dominant influence on the permeability, thus the permeability coefficient of the remolded loess decreased slowly. Furthermore, under identical salt content, the changes in the pore water occurrence status and pore structure of the calcium salt remolded loess were more significant than those in the sodium salt remolded loess.