Building structures on clayey soil presents unique challenges to geotechnical engineers due to the inherent variability in clayey soil consistency. Understanding engineering properties of clayey soils is essential for accurate geotechnical design and the prevention of potential issues such as settlement and instability. The current study provides crucial insights for geotechnical assessments and engineering solutions in the area, highlighting key soil properties that affect the classification of clayey consistency. Advanced machine learning (ML) models were employed to predict the in situ clay consistency, a vital parameter for evaluating the deformation resistance of clayey soils under structures. The ML predictions are based on nine features representing the physical and mechanical properties of the clay, which are easily determined through laboratory and field evaluations. A dataset comprising 173 samples is compiled, which extracted from Nile Delta in Egypt, incorporating data on the basic properties of the soils to train and test several ML classification algorithms. The classification models, including logistic regression, k-nearest neighbors, support vector machine, random forest, and gradient boosting classifiers, are evaluated using metrics such as accuracy, sensitivity, specificity, and F1-score. The results demonstrate that the gradient boosting classifier model exhibits the highest accuracy in predicting clay class, achieving 97% and 86% accuracy for the training and testing datasets, respectively. These findings offer a valuable framework for efficiently and cost-effectively classifying clays, assisting geotechnical engineers in making informed decisions about foundation design and construction on clayey soils. Additionally, the study establishes equations to predict the undrained shear strength of clayey soil based on its basic properties, providing a practical and accurate method for estimating soil strength characteristics. These contributions enhance the understanding and management of clayey soil behavior in geotechnical engineering, offering essential guidance for foundation design and construction projects in clayey soil regions.

To improve the crop yield of low-yield Albic soil, the application of amendment materials has become a widely considered method. However, understanding how these materials impact the physical and mechanical properties of the soil for tillage purposes is an important area of research. This study aimed to examine the effects of fertilizers, straw, and biochar on the tillage characteristics of Albic soil. The focus was on analysing changes in soil consistency limits and cultivability in both the humic (Ap) layer and the Albic (Aw) layer, while also exploring the underlying mechanisms. The results showed that the use of amendment materials significantly improved the consistency limits of Albic soil, enhanced its cultivability, and positively affected its tillage characteristics. These improvements were reflected in a decrease in the soil's plasticity index (PI) and an increase in the shrinkage index (FI). Among the three materials tested, biochar had the most notable impact on plasticity, with significant increases in the liquid limit (LL) and plastic limit (PL), while straw primarily influenced the swell-shrink characteristics, leading to a significant decrease in the shrinkage limit (SL). The Aw layer was more significantly impacted by the amendment materials than the Ap layer. This was largely owing to the strong positive correlation between the Brunauer-Emmett-Teller (BET) surface area, soil maximum hygroscopicity (W), and LL and PL of the Ap layer, as well as their negative relationship with the PI. In contrast, the Aw layer was most influenced by organic matter content (OMC) and soil organic carbon (SOC). It is important to note that the addition of fertilizer or straw at concentrations above 6% by weight could lead to different changes in the tillage characteristics of Albic soil. This study provides valuable insights for agricultural practice, offering guidance on overcoming soil-related challenges in tillage operations, and it also opens new possibilities for a comprehensive, multi-faceted approach to soil management.

The tangential displacement amplitude determines the mobilization of shear strength and the deforming and sliding displacements of soil-structure interfaces, and therefore plays a crucial role in the interface behavior. A series of three-dimensional (3D) simple-shear interface tests were conducted between gravel and steel to investigate the influence of tangential displacement amplitude on the tangential deformation, volumetric change, and shear strength. Test results show that deforming and sliding displacements are distinctly induced by shearing. The deforming displacement migrates toward the initial shear direction, caused by the shear orientation effect, and the migration becomes magnified and then stabilizes with cyclic shearing. The shear strength would not be mobilized when the tangential displacement amplitude is relatively small. It behaves in an anisotropic manner if mobilized and gradually degrades as cyclic shearing continues, attributed to the dominant particle crushing over the shear densification effect. Two critical tangential displacement amplitudes are found for the mobilization of shear strength, and determine whether the shear strength could be mobilized during cyclic shearing and whether it is immediately mobilized at initial shearing, respectively. The tangential displacement amplitude primarily affects deforming and sliding amplitudes and their migration, shear stiffness, irreversible and peak reversible normal displacements, peak and residual cyclic shear strength, and anisotropy extent, instead of their relationship patterns. An increased tangential displacement amplitude results in magnified sliding amplitude, decreased deforming weight, accelerated degradation of deforming amplitude, and magnified migration of deforming and sliding displacements. Additionally, large tangential displacement amplitude leads to large irreversible and peak reversible normal displacements, small shear stiffness, and small peak and residual cyclic shear strength. The peak reversible normal displacement is determined by and has a linear relationship with the deforming displacement, and the irreversible normal displacement presents perfect consistency behavior against shear work density, regardless of tangential displacement amplitude. The consistency behavior could be well described using a hyperbolic model, which significantly simplifies the 3D constitutive modeling of the interface.

Some soil behaviors change significantly as water content varies over time. The particle size distribution of soils has a direct impact on mechanical properties such as soil water content, resistance to dispersion, swelling-shrinkage, fluidity, plasticity, and stickiness. This study was conducted to investigate the usability of Atterberg limits, consistency index and coefficient of linear extensibility (COLE) in the temporal planning of ecosystem restoration activities such as silvicultural interventions, tillage, afforestation, and the construction of forest roads, etc. Surface soil samples were collected from the sections numbered 263, 264, 266, 268, 317, 318, 319, 323, 324,325 and 366 of the degraded forest of the And & imath;r & imath;n forestry operations department. The COLE, liquid limit (LL), plastic limit (PL), plasticity index and consistency index values of soil samples were determined. The LL values ranged from 17.5 to 62.4%, the PL values from 8.2 to 46.8% and the PI values from 6.4 to 15.5. The highest COLE value (0.13) was recorded in the 318, while the lowest COLE value (0.03) was in 325.The LL and PL values have a positive linear relationship with clay and organic matter content. All sections have karstic characteristics, but the mechanical characteristics of the soils differ significantly between the sections. Silvicultural interventions carried out especially in 318, which had the lowest consistency index (Ic = 0.70), and sections 263, 264, 317 and 319, where the consistency index is >2,should take mechanical properties into account, and the planting time intervals should be determined, accordingly for sustainable forestry.

As the first purely multi-decadal satellite-based soil moisture product that spans over 35years (from November 1978 to December 2013) on a daily basis designed for climate application, the applicability of the European Space Agency (ESA) soil moisture product, including the hydrological consistency between the product and the observed precipitation and the product continuity on the Tibetan Plateau (TP) were investigated. The results show that there is significant degree between the ESA soil moisture product and the observed precipitation. The positive anomaly of the ESA soil moisture product can reflect the occurrences of precipitation, but the precipitation may not definitely lead to soil moisture anomaly, which largely depends on the precipitation amounts. For climate application, large number of missing gaps was shown on the west of the TP, where it is considered that the retrieval algorithms are largely affected by the permafrost covered in this region, leaving the ESA soil moisture product for further improvement. In application, the ESA soil moisture product was used to study the response of surface soil moisture to climate change on the TP. With the rapid warming and the overall wetting of the TP, soil moisture increases on the central of the TP with the increase of precipitation, and decreases in the southeast TP with the precipitation deduction. However, it decreases in the west TP, where it was probably influenced by both the insignificant precipitation changes and the significant increase of evaporation.