Expansive clays with high plasticity need to be stabilized to prevent hazards that may arise due to the extreme volume changes experienced with moisture fluctuations. Utilizing a kind of natural and eco-friendly sustainable fiber named as basalt fiber into the soils has become a new issue that needs to be expanded in scope. In this paper, a high plastic soil was stabilized by these natural basalt fibers to reduce possible soil-induced disasters. Basalt fibers in different lengths were mixed into the clay at varied amounts. Due to the soil’s sensitivity to water, the samples were prepared at distinct water contents, 2 on the dry and 3 on the wet side of the optimum. To question whether the strength loss due to the moisture change can be regained with basalt fibers or not, the strength tests were performed on both natural and stabilized samples. Through the tests, it was revealed that the strength of the expansive clays can be enhanced up to 280% at a fiber content of 2%. The highest strength was obtained at approximately 880 kPa by mixing 24 mm fibers with 15% water at 1 and 2% ratios. As anticipated, the long fibers (24 mm) supplied a real reinforcement even at high water contents. In addition, the obtained data set was used to train machine learning algorithms (linear, ridge, lasso, support vector, decision tree) that have just started to be applied in geotechnical engineering. Results have proved that, the decision tree regression outperformed the stress and strain with 0.85 R-squared (R²) in stress and 0.91 R² in strain estimation. Additionally, it was revealed from the feature importance analyses that water content has an importance of approximately 85% on stress and up to 97% on strain.

A soil’s physical properties, mineral types, and pore structure significantly influence the shape and properties of the soil-water characteristic curve (SWCC). This study investigated the effects of the soil’s physical properties and mineral types on the SWCC and pore-size distribution (PSD). Eight different soils from an alluvial deposit in Istanbul and Adapazarı/Türkiye were used in the study. The test samples were prepared by compaction at optimum water content (OWC) and wet side of optimum water content (wet of OWC). The samples were prepared by consolidation from the slurry. The PSDs of the samples were calculated using the SWCCs and evaluated with scanning electron microscope (SEM) analysis. In addition, the mineral types of all soils were determined by X-ray diffraction analysis. The soil which contains illite-type minerals has higher matric suction than containing kaolin-type. The effect of the clay percentage is more pronounced in silty soils than in plasticity and activity. Soil suction increased with decreasing compaction water content in clayey soils. The air entry water contents rose as the void ratio, liquid limit, clay content, and plasticity increased. The compaction conditions affected the macropore structure more than the micropore structure. In addition, the ratio of macro-micro pore sizes increased with the rise of the compaction water content.

Industrialization and population growth have made surface areas more valuable, thereby the multi-story buildings have become an absolute necessity. At this point, numeric models became the fastest and simplest way to evaluate the response of soils and structures. The issued factor in the current paper is related to the way of transferring the multi-story building loads to an alluvial stratum and evaluate the accuracy of different cases, in order to save time and economy. For load transfer, the first case (case i) includes uniform distributed load, the second case (case ii) includes the transfer from the basement columns and walls, and the third case (case iii) includes modeling the real state of the building. Mainly, all three cases gave close results in terms of settlement magnitudes of 2.21, 1.96, and 1.81 cm, respectively. It was inspected that case (i) showed 12.8% more deformation than case (ii) and 22.1% more deformation than case (iii). However, the situation is not the same for the settlement pattern, and the under-column and corner effects are neglected in uniform load. Additionally, the bending moments, which is a critical parameter for the design of a reinforced concrete foundation, have developed different results. In case (ii) and (iii) a bending moment of 500 kNm/m is observed in the center column, while in case (i) the moments converge to 0. Therefore, this study highlights the importance of outstanding decision making when assessing the load-transferring mechanism in modeling with numerical methods. The necessity of the determination of the convenient load transfer way depending on the parameter that is crucial in the evaluation of the soil–structure interaction comes to the fore with current paper.

Current deep excavation applications, which pose risks for constructing high-rise buildings and infrastructures, are increasing. Therefore, the increasing urbanization, underground infrastructure requirements, and time and cost constraints in construction projects have led to a growing demand for rapid, economical, and safe deep excavation designs. Although numerical modeling tools enable rapid analyses, the reliability of soil engineering parameters remains a challenge due to natural variability, sample disturbances, and differences between laboratory and field test conditions. In this study, PLAXIS 2D (Version 24) was used to model a deep excavation, allowing for the assessment of soil–structure interaction and excavation-induced deformations. The objectives are to compare field data with the numerical model and identify which soil parameters are critical for excavation. Through the sensitivity analysis, the study highlighted that the variations in shear strength parameters, such as cohesion and internal friction angle, are crucial and shall be precisely determined. The performed analyses revealed that even minor changes in the internal friction angle can dramatically impact displacements by doubling them and highlight the significant disparity between the minimum and maximum margins. The numerical analysis underscores the need for precise parameter measurement and careful analysis to achieve reliable results and ensure safer, more effective designs. The comparison of numerical results with field measurements confirmed the model’s accuracy.