Matric potential variation and frost heaving in unsaturated loess during freezing process

The frost heave characteristics of loess directly affect the engineering stability in loess regions. In expressway embankments with loess fill material, significant frost damage occurs due to high fill height and water accumulation at the base. This study investigates frost heave deformation of loess samples with varying initial saturation through unidirectional freezing tests coupled with matric potential measurement. The frost heave deformation characteristics of unsaturated loess during freezing are analyzed from the perspective of internal matric potential variation. Experimental results demonstrate that initial water content substantially regulates the freezing process. Each 5% increase in water content prolongs temperature field stabilization by approximately 4-5 hours. Furthermore, high-water-content specimens exhibit approximately 42% greater final freezing depth. Moreover, matric potential evolution synchronizes with frost heave development. In low-water-content (10%) specimens, matric potential plunges from 0.1 kPa to -1920 kPa within 18 hours. This drives rapid moisture migration toward the freezing front and subsequent segregation ice formation. Frost heave evolution is governed by dynamic equilibrium between matric potential and gravitational potential. Frost heave terminates when these two potentials reach equilibrium. This research provides crucial technical support for expressway construction and maintenance in loess regions.