In this paper, salt expansion tests were conducted on coarse-grained sulfate soils to investigate salt expansion characteristics. The experimental results indicate that the formation and growth of salt crystals are influenced by environmental temperature and humidity; during the cooling process, the specimen expands due to the growth of salt and ice crystals. The heave in the positive temperature range increases with increasing sulfate content, while the heave in the negative temperature range reaches a peak value when the salt content varies between 0.4% and 0.7%, indicating that the combined effect of precipitation and freezing contributes to significant volumetric expansion. The initial precipitation temperature increases with increasing pore solution concentration before it reaches 30°C. The freezing point is influenced by soil particles, pore solution concentration, and initial water content. The freezing point first decreases with increasing salt content and tends to be stable afterward when the water content is relatively high. However, the freezing point exhibits a continuous decreasing tendency if salt crystal precipitation occurs before freezing. An empirical model is proposed to predict the salt heave ratio in the positive temperature range based on salt crystal volume changes, and the relationship between the precipitation and freezing processes in the negative temperature range is examined.

Phase composition curves are the basis for the thermo‐hydraulic analysis of saline soil in cold regions. Two types of phase transition, namely, the water‐ice and solution‐crystal phase transitions, would occur in saline soils due to the variation in temperature and migration of moisture and solute, and the occurrence order of the two types of phase transition is governed by the initial salt and water content. This study proposed a conceptual model for the water phase composition curve in saline soils by simplifying the correlation between pore solution properties and soil grain. This model was subsequently applied to the analysis of phase composition characteristics and explained the occurrence of a second phase transition in saline soil. The model was validated by the experimental data from known soils and showed both good results and ease of use when compared to three previous models. The conceptual model provides a convenient and intuitive way to understand the phase composition characteristics of pore solution in saline soil in cold regions and is also easy to use in the thermo‐hydraulic analysis such as the prediction of unfrozen water content and solute concentration.

The load and settlement histories of stage-constructed embankments provide critical insights into long-term surface behavior under embankment loading. However, these data often remain underutilized in predicting post-construction settlement in the absence of geotechnical subsoil characterization. To address this limitation, the current study integrates bidirectional long short-term memory (BiLSTM) into a three-phase framework: data preparation, model construction, and performance evaluation. In the data preparation phase, the feature vector comprises basal pressure, pressure increments, time intervals, and prior settlement values to facilitate a rolling forecast. To manage unevenly spaced data, an Akima spline standardizes the desired time intervals. The model’s efficacy is validated using observational data from two distinct construction case studies, each featuring diverse soil conditions. BiLSTM proves effective in identifying key attributes from load and settlement data during the staged construction process. Compared to traditional curve-fitting methods, the BiLSTM model exhibits superior performance, robustness, and adaptability to varying soil conditions. Additionally, the model demonstrates low sensitivity to the range of post-construction data, allowing for a data collection period reduction—from six months to three—without compromising prediction accuracy (relative error = 0.92%). These advantages not only optimize resource allocation but also contribute to broader sustainability objectives.