Generally, brick buildings are in the open-air environment year round, and damage to them is aggravated by the effect of repeated freezing and thawing cycles. In order to determine freeze–thaw damage and deterioration mechanism, the initial moisture content of gray brick specimens was set as 20%, 40%, 60%, 80%, 100%. The effects of moisture content and the number of freeze–thaw cycles on the quality, mechanical properties and microstructure of gray brick were investigated by uniaxial compression tests and scanning electron microscopy (SEM) tests. Numerical simulations were applied to model the freezing and thawing process. The results showed that: as the number of freeze–thaw cycles increased, the mass loss rate and peak strength reduction rate of gray brick both increased. The initial moisture content had a greater impact on damage to gray brick due to freeze–thaw; ω = 80% was defined as the limit moisture content of gray brick. Under the repeated action of freeze–thaw cycles, the areas affected by thermal stress were mainly concentrated in the center of the outer surface and the center of the side of gray bricks. The maximum thermal stress after 55 freeze–thaw cycles was 1.522 × 10⁻² MPa. This research results provide a theoretical basis for the prevention and protection of frost damage of brick buildings in a freeze–thaw environment.

Soil classification and analysis are essential for understanding soil properties and serve as a foundation for various engineering projects. Traditional methods of soil classification rely heavily on costly and time-consuming laboratory and in-situ tests. In this study, Support Vector Machine (SVM) models were trained for soil classification using 649 Cone Penetration Test (CPT) datasets, specifically utilizing cone tip resistance (\(q_c\)) and sleeve friction (\(f_s\)) as input variables. Pearson correlation and sensitivity analysis confirmed that these variables are highly correlated with the classification results. To enhance classification performance, 25 optimization algorithms were applied, and the models were validated against an independent dataset of 208 CPT records. The results revealed that 23 of the algorithms successfully improved the SVM classification accuracy. Among these, 18 algorithms achieved higher accuracy than the current engineering standard, the “Code for in-situ Measurement of Railway Engineering Geology.” Notably, the Thermal Exchange Optimization (TEO) algorithm resulted in the most significant improvement, increasing the accuracy of the original SVM model by 10% and exceeding the standard by 4.3%. Moreover, the models were thoroughly evaluated using Monte Carlo simulations, confusion matrices, ROC curves, and 10 key performance metrics. In conclusion, integrating evolutionary algorithms with SVM for soil classification offers a promising approach to enhancing the efficiency and accuracy of soil analysis in engineering applications.

Fracture characteristics are the basis of silty clay fracture research, and its quantitative description is helpful to explore the engineering properties of silty clay. The silty clay samples with different moisture contents and different aspect ratios were prepared by the controlled variable method for the drying shrinkage test. The crack image processing and crack feature extraction were performed by PS and IPP software, and the relationship between the crack propagation characteristic parameters and the change in humidity and sample moisture content during drying shrinkage were analyzed to explore the crack development law. The results show that under the continuous action of the environment, cracks were generated at the initial high temperature (46 °C). When the temperature changed from a high temperature (46 °C) to a low temperature (27 °C), the moisture content decreased faster, and the crack developed rapidly. Later, from low temperature (12 °C) to high temperature (46 °C), the water content and crack parameters remained basically unchanged; the cracks of the samples with a high moisture content appeared early, developed rapidly, and damaged seriously. When the aspect ratio was 6:1, the crack developed vertically, and when the aspect ratio was less than 6:1, the secondary crack was about 90° from the upper crack.