Horizontal frost heave disasters frequently occur in cold-region engineering projects, making it essential to understand water migration mechanisms along horizontal directions during freezing processes. Using a selfdeveloped one-dimensional visualization horizontal freezing apparatus, unidirectional horizontal freezing tests were conducted on soft clay under varying temperature gradients, and the development process of the cryostructures was continuously observed. The results indicate that the thermal-hydraulic processes, including temperature evolution, water content variation, pore-water pressure dynamics, and soil pressure changes, demonstrate similarities to vertical freezing patterns, with temperature gradients primarily influencing the magnitude of parameter variations. Under the influence of gravity, the freezing front forms an angle with the freezing direction, attributed to differential freezing rates within soil strata. Post-freezing analysis showed dualdirectional water redistribution (horizontal and vertical), with horizontal migration dominating. Maximum water content was observed 1-3 cm from the freezing front. Distinct cryostructures formed in frozen zones were identified as products of tensile stresses generated by low-temperature suction and crystallization forces. The study highlights the coupling of water transfer, thermal changes, mechanical stresses, and structural evolution during freezing and suggests that water migration and cryostructure formation are interrelated processes. This research provides robust experimental evidence for advancing the theoretical framework of horizontal water migration mechanisms in frozen soil systems.

Diurnal freeze-thaw process occurs in the Lianghekou area in winter, which will affect the construction progress and quality of the project. In this paper, the compressibility of clay experiencing the freeze-thaw (F-T) cycles under different impacting factors was investigated. A series of unidirectional F-T tests were carried out in a closed system, and the compressibility tests were carried out for the same specimens underwent F-T cycles to study the compressibility along the specimen height. The experimental results demonstrate that the initial moisture content of specimens, the cooling temperature, and the number of F-T cycles affect the compressibility of specimens. As the cooling temperature decreases, the initial moisture content or the number of F-T cycles increases, the compressive strain of the affected zone of specimens increases under the same vertical pressure, while the confined compressive modulus decreases. The variation of the compressibility for the unaffected zone is different from that for the affected zone. For the same impacting factor, the compressive strain of the affected zone is greater than that of the unaffected zone, while the confined compressive modulus of the former is less than that of the latter. The change of compressibility is mainly affected by the characteristics of cryostructure and moisture migration of the specimen after F-T. This research may provide some guidance for the engineering construction process in winter in the seasonally frozen ground region.

Permafrost is an important part of the cryosphere, playing an integral role in the hydrologic cycle, ecology, and influencing human activity. Melting of ground ice can drastically change landscapes and associated thaw subsidence may induce instability of infrastructure. The terrain conditions on the Qinghai-Tibet Plateau are complex, and the spatial distribution of ground ice is highly variable, so knowledge of its abundance and variability is required for impact assessments relating to the degradation of permafrost. This study examined 55 permafrost samples from warm, ice-rich permafrost region in Beiluhe Basin, Qinghai-Tibet Plateau. The samples were examined using Computed Tomography scanning, and the ice content and cryostructure were determined. The results indicated that: 1) variation in volumetric ice content was considerable (0%-70%), with a mean value of 17%; 2) seven cryostructures were identified, including crustal, vein, lenticular, ataxitic, reticulate and layered cryostructure; 3) volumetric ice content varied by cryostructure, with the highest associated with layered and ataxitic cryostructures. Volumetric ice contents were lowest for samples with pore and lenticular cryostructures. This work provides detailed ground ice content and will be helpful for assessing thaw subsidence and infrastructure stability on Qinghai-Tibet Plateau.

The excess ice content of near-surface permafrost near Barrow, Alaska, was estimated using cores collected from 57 drained thermokarst-lake basins and additional cores from a nearby landform unaffected by thaw-lake processes. The excess ice content, estimated using soil cryostructures, increased with surface age: from 20 per cent in young basins?