The influence of different proportions of clay minerals on the moisture density relationship and index properties of clay soils are not clearly understood because of the different factors that come into play in natural soil formation. This study used 11 different remolded samples prepared by combining double mixtures of commercially available powdered kaolinite, montmorillonite and quartz in proportions of 30%, 50%, 70% and 100% based on dry unit weight to investigate the relationship between different proportions of clay minerals with index properties and compaction characteristics of clay soils. The results described the influence of different proportions of clay minerals on the liquid limit, plastic limit and plasticity index measured using the fall cone penetration test. Also, the variation of maximum dry density and optimum moisture content with different clay mineral proportions has been analyzed. In addition, equations are presented with significant correlations to show the relationship between Atterberg limits, compaction parameters and the proportion of clay minerals. Knowledge on the effect of the different clay minerals on the moisture density relationship and index properties can be used to predict the behavior of compacted clay soils encountered in engineering practices and reduce the time and effort needed for assessing the suitability of clay soils and clay liners for engineering use.

The behaviors of high‐plasticity clays depend largely on the clay mineral content. Recently, it has been observed that sudden slope failures of most clay slopes occur in regions pronounced with repeated rainfall and sunny climate. The reason for this is still unclear. Examining the effect of clay minerals and drastic weather changes on shear strength will be useful in predicting the performance of structures built in such soils and to take precautionary measures to improve the properties before failure. Therefore, a series of quick direct shearing tests were conducted on 11 artificial clay mixtures. The cohesion and frictional strength properties were determined and linked to the proportion of clay minerals and the number of wetting and drying cycles. The results show a significant reduction in shear strength after exposure to wetting and drying. Generally, montmorillonite‐dominated mixtures were less susceptible to the changes in cohesion strength than kaolin‐dominated mixtures, and the reduction in frictional strength was relatively insignificant.

Three‐dimensional finite element method analysis on the tunnel‐soil‐underground pipeline was carried out based on the ABAQUS program. PSI element was applied to simulate the interaction between the pipelines and soil. Parameters such as an elastic modulus of soil, stress release rate, at‐rest lateral pressure coefficients, an elastic modulus of pipelines, and buried depths of tunnels were analyzed. The effects of tunnel excavation on the displacement of existing pipelines were investigated, and the settlement relationships were obtained. The relationship between each parameter and surface settlement was determined by the grey relational analysis method to analyze each parameter’s sensitivity to the settlement of the pipeline, which can provide a reference for emphasis and methods of shield tunneling support. Finally, a formula of the settlement relationship between the maximum surface settlement and pipelines deformation was proposed for different pipe‐soil relative stiffness. The formula was applied in the practical case. Compared with the field monitoring results and FEM computer results, it has been found that the proposed normalized formula is consistent with the measured results and numerical simulation of the pipeline settlement.

Slope instability in mountainous regions poses serious challenges to infrastructure resilience, particularly under anthropogenic pressures and climatic variability. This study evaluates the mechanical reinforcement provided by Vetiver (Chrysopogon zizanioides) to stabilize slopes in seven representative soils of the Quillollaco Formation, southern Ecuador. Direct shear tests on soil–root composites were used to quantify root-induced improvements in cohesion (c′) and internal friction angle (ϕ′), and slope stability was analyzed with the Spencer limit equilibrium method for heights of 5, 10, and 15 m under dry conditions. Results demonstrated significant reinforcement effects, with Vetiver increasing shear strength parameters at all depths and maintaining safety factors above 1.10 in every scenario. The highest gains, up to 16%, were observed in high-plasticity soils (CH and MH). Sensitivity and inferential statistical analyses confirmed the robustness of these improvements, with over 95% of paired t-tests yielding p < 0.05. These findings highlight Vetiver as a reliable nature-based solution for slope stabilization in tropical mountain environments, offering a sustainable and transferable alternative to conventional geotechnical methods.

A true triaxial testing apparatus with rigid compound and sophisticated loading system was applied to carry out series of tests to study the stress-induced anisotropy of sand under three dimensional stress states. The additional loads were applied from σ₁, σ₂, and σ₃ direction based on initial three dimensional complex stress states. The different stress and strain relationships in different directions were investigated. Stress-strain matrix was studied by analyzing the measured stress and strain in different principal directions. It was found that there is remarkable anisotropic stress and strain behavior in different principal directions which is much different from traditional triaxial testing results.

Permanent ground deformations associated with earthquakes, liquefaction and landslides can introduce substantial axial and bending strains on buried pipeline systems. The analysis of the strains is largely dependent on the force imposed on the pipeline by relative displacement between the pipeline and surrounding soil. To advance state-of-the-art for soil continuum models, it is necessary to develop better simulation of soil-pipeline interaction. In this study, finite element analyses (FEA) of the soil-pipe interactions under lateral movement in dry sand are investigated. Mohr-Coulomb strength parameters applied in FEA are developed from direct shear test data and a subroutine was introduced to represent strain softening. The results show excellent agreement with large-scale 2D experimental results and the results are used to construct a dimensionless chart for various depth-to-diameter ratios for dry sand. The favorable agreement between analytical and experimental results marks a transition from characterizing engineering behavior through experimental results to characterizing that behavior on the basis of computational simulation. The guideline based on experimental results for estimating force induced by soil-pipeline interaction can be replicated with FEA.