Geotechnics, Volume 5, Issue 4 (December 2025) – 15 articles

Yamamoto’s theoretical solution for a two-dimensional wave-induced response of an elastic seabed with finite permeability needs a simultaneous equation to be solved. Analysis of the dimensionless simultaneous equation demonstrated that it becomes unsolvable due to the singularity of its matrix when the permeability coefficient of the seabed approaches infinity and zero, representing (elementwise) fully drained and undrained conditions, respectively. To address this limitation and thus expand the verifiable drainage condition for a finite element analysis code, theoretical solutions for seabed responses under the fully drained and undrained conditions were derived. The feasibility of these solutions was discussed through comparison of the forms of these solutions with the one of Yamamoto. Furthermore, characteristics of seabed behaviors explained by these solutions were obtained. Finally, these theoretical solutions and Yamamoto’s solution were utilized to verify a finite element analysis code by considering horizontally periodic seabed behavior in the numerical analysis. It turned out that the numerical code was capable of expressing seabed behavior in any drainage condition without any approximation to a governing equation as made in the derivation of the fully drained and undrained solutions. Therefore, the numerical analysis code is now reliably used for further studies on wave-induced seabed behaviors even out of the verifiable range of drainage conditions by Yamamoto’s solution. Full article

Partially frozen soil (PFS) is composed of coexisting unfrozen water and ice within its pores at subzero temperatures. This review paper examines how unfrozen water content (UWC) and pore ice content interact during phase changes under near-freezing conditions, governed by microscopic thermodynamic equilibrium. We present key theories describing why UWC persists (premelting, disjoining pressure) and the soil freezing characteristic curve (SFCC), along with measurement techniques, including the gravimetric approach to advanced nuclear magnetic resonance for characterization of water content. The influence of the water–ice phase composition on mechanical behavior is discussed, signifying pore pressure and effective stress. Various modelling approaches categorized into empirical SFCC, physio-empirical estimations, and emerging machine learning and molecular simulations are evaluated for capturing predictions in PFS behavior. The relevance of PFS to infrastructural foundations, tailing dams, permafrost slope stability, and climate change’s impacts on cold regions’ environmental geotechnics is also highlighted as a challenge in practical application. Hence, understanding pore pressure dynamics and effective stress in PFS is critical when assessing frost heave, thaw weakening, and the overall performance of geotechnical structures in cold regions. By combining micro-scale phase interaction mechanisms and macro-scale engineering observations, this review paper provides a theoretical understanding of the underlying concepts vital for future research and practical engineering in cold regions. Full article

Existing pile foundations in the Arctic face significant limitations regarding bearing capacity, environmental impact, and dismantling capabilities. This study proposes and geomechanically justifies a novel technology for constructing dismantlable modular pile foundations in permafrost using a pile with a dome-plug (PDP). Comparative numerical modeling was conducted to analyze the bearing capacity of the proposed PDP versus a conventional pile without a dome-plug (PWDP) across six types of frozen rocks (clays, loams, sandy loams), specifically accounting for salinity. The results indicate that the dome-plug effectively transforms the shell pile into a combined pile-column, providing a bearing capacity increase ranging from 35% to 63%. Notably, the highest relative improvement was observed in the weakest saline rocks. The proposed technology serves as a superior alternative to traditional piling methods, enabling the deployment of modular foundations as a cost-effective and eco-friendly substitute for artificial soil islands. Full article

This study investigates the influence of stratification—the vertical layering of particles with different sizes—on porosity in granular sediment packings. Conventional porosity models are typically formulated for homogeneous, well-mixed grain assemblies; however, natural riverbed sediments often exhibit stratification, leading to deviations from these idealized conditions. Part I established empirical relationships describing transition layer geometry and porosity in systems composed of low-friction glass beads. Building on this foundation, Part II extends the analysis by incorporating the higher inter-particle friction characteristic of natural sediments, using discrete element method (DEM) simulations to quantify its effect on packing structure and porosity. A refined method is used to extract porosity and density distributions from simulated packings, enabling accurate identification of transition layers. Empirical formulas are developed to predict key transition-layer parameters (thickness, average porosity, and minimum porosity) as functions of the grain-size ratio. A density-based porosity prediction model is introduced and coupled with an existing model for well-mixed sediments, allowing for a quantitative comparison between stratified and homogeneous packing scenarios. Results show that stratification can increase porosity by 44–57% relative to well-mixed samples of an identical grain-size composition. These findings highlight the importance of considering sediment stratification when modeling riverbed porosity and pave the way for improved sediment transport and hydraulic predictions. Full article

This study investigates how stratification—layering of particles of different sizes—affects porosity in granular sediment packings. While most existing porosity models are developed for well-mixed, homogeneous grain structures, natural riverbed sediments can be stratified, which may lead to significant deviations in porosity. To address this, a novel, cost-effective, and non-destructive laboratory method was developed to measure the vertical porosity distribution in stratified samples using glass beads. Results confirmed the presence of transition layers at the interface between coarse and fine sediments, where porosity follows a distinct trend of decrease and recovery. A Discrete Element Method (DEM)–based simulation model (Particula 1.3) was calibrated and validated against laboratory results, enabling broader parameter studies beyond the physical experiments. An improved algorithm based on a density threshold was also introduced to efficiently and objectively determine the transition layer extent in simulations. Empirical formulas linking transition layer thickness and porosity metrics to the grain-size ratio were derived, enabling the calculation of the average porosity of a stratified sample. Part I focuses on the experimental setup, model validation, and foundational insights into transition zone formation. A companion paper (Part II) will build on these results to develop predictive models for porosity in stratified sediment. Full article

The offshore wind industry is expanding from shallow water to deep water. As a cost-effective and efficient anchoring solution, drag embedment anchors have been widely used for mooring floating offshore structures. However, there is currently no well-established method for predicting the installation trajectory and holding capacity of drag anchors in sand. This paper reports an integrated anchor–chain–soil large-deformation finite-element model for simulating the complete installation of drag anchors in sand. The proposed approach restores the effects of anchor chains and detailed structures of the anchor, which is essential for detailed anchor design. Sensitivity analysis is conducted to investigate the convergence of model parameters. The performance of the numerical model is benchmarked against a centrifuge test conducted at the University of Western Australia (UWA), which demonstrates satisfactory accuracy and reliability. Installation simulations are then performed using a popular commercial anchor design in sands of different friction angles. Three characteristic stages during the drag embedment process are identified. The results highlight the significant influence of the soil resistance to the shank on the anchor penetration performance. The large-deformation analysis approach proposed provides a powerful tool for further investigation on drag anchor installation behavior in sand. Full article

The reuse of rubber inclusions obtained from End-of-Life Tires (ELTs) offers both environmental and technical benefits in civil engineering applications, reducing landfill disposal and enhancing the dynamic properties of geomaterials. The use of well-graded Gravel–Rubber Mixtures (wgGRMs), produced by blending well-graded gravel with granulated rubber, has been investigated for use in different geotechnical applications. The percentage of rubber inclusions included in wgGRMs significantly modifies the mechanical response of these mixtures, influencing stiffness, strength, dilatancy and dynamic properties. Due to the material heterogeneity (i.e., stiff gravel and soft rubber), the effective implementation of wgGRMs requires the development of constitutive models that can capture the non-linear stress–strain response of wgGRMs subjected to representative in situ loading conditions. In this study, a critical state-based generalized plasticity model is presented and tailored for wgGRMs. Calibration is performed using experimental data from isotropically consolidated drained triaxial tests on wgGRMs with different rubber contents. It is shown that the model accurately reproduces key features observed experimentally, including post-peak strain softening, peak strength variation, and volumetric changes across different confining pressure levels and rubber content fractions. This model represents a useful tool for predicting the behavior of wgGRMs in engineering practice, supporting the reuse of ELT-derived rubber. Full article

In recent years the Government of the Sultanate of Oman has planned the construction of recharge dams in the semi-desert region of Wilayat Ibri, according to the growing domestic water demand for drinking and agricultural use. For this reason, the Engineering Company SERING International planned the construction of rockfill dams, well positioned according to the local morphological and geological context. Using temporary floodwaters and releasing them slowly downstream, these dams increase the water flow of the Aflaj. The latter is the existing traditional irrigation system devised to manage the scarce water resources of the Sultanate. In this paper, we describe the IBRI 14 Dam, namely Wadi Sulayf Dam, with a total length of about 3200 m and lying close to the settlements of Ibri Town, the largest one among those projected. This paper shows the criteria that guided the design studies of the dam linked to the geological and geotechnical features of the area, the main dam characteristic and the activities developed until the work was completed in 2020. This work represents an interesting and useful case study about the complete cycle of realization of a dam, in particular considering that it had been affected by huge flooding during the construction but reporting no significant damage. Full article

This work stems from the curiosity stimulated by a paper by Yttrup and Abramsson, which appeared in the journal Australian Geomechanics in 2003. Their work proposes a kinematic limit analysis method to compute the ultimate strength of steel screw piles in sand when first the bending and then the plastic collapse of the pile helix occurs. It is accompanied by insightful comments drawn from geotechnical design experience. The paper has both academic and professional impact as it is cited in scientific journals and used in engineering practice in Australia and New Zealand. However, the original paper is quite brief in its exposition. Here, Yttrup and Abramsson’s model is critically reconstructed, providing guidance that can help avoid potential pitfalls in its application. A variation of the model is proposed. Then, the calculated results are discussed and compared with experimental results, starting with those of the original paper. This work hopes to contribute to enhancing the appraisal, adoption, and utility of Yttrup and Abramsson’s model in design practice and in subsequent studies. Full article

Many immersed tunnels are constructed in alluvial formations within earthquake-prone regions, making seismic resistance a critical aspect of their safety design. During an earthquake, tunnel displacements can lead to slippage between the tunnel and surrounding soil and may be further amplified by liquefaction. This phenomenon can cause severe structural damage, including tunnel flotation. This paper examines the seismic performance of immersed tunnels, starting with an overview of the deformation mechanisms affecting tunnels, including those induced by ground shaking and failure. Given its significance in large foundation deformations and its impact on tunnel integrity, liquefaction is analyzed alongside potential mitigation strategies. The seismic design process for immersed tunnels is discussed in detail, covering analytical approaches, numerical modeling techniques (such as finite element and finite difference methods), and physical modeling. Real-world examples are provided to illustrate key concepts. Finally, this paper summarizes the core factors influencing the seismic response of immersed tunnels and highlights future research directions to enhance their resilience in seismic environments. Full article

Improper disposal of waste tires has led to significant environmental and economic challenges, including pollution and inefficient resource utilization. The growing focus on sustainable solutions in geotechnical engineering highlights the potential of sand–rubber tire shred mixtures for applications such as soil stabilization, embankment reinforcement, seismic isolation, and drainage. This paper presents a bibliometric study analyzing research trends, methodologies, and applications of these mixtures from 2000 to 2025, based on 366 relevant publications. The findings indicate a substantial increase in publications after 2015, reflecting heightened academic and industrial interest in sustainable construction materials. Keyword co-occurrence analysis reveals key research themes, including optimization of shear strength, enhancement of compressibility, and mitigation of seismic impacts. Citation network maps illustrate influential studies and collaborative research networks that are propelling advancements in this field. Despite the advantages of sand–rubber mixtures, challenges such as compaction difficulties, variability in rubber particle size, and long-term durability remain to be addressed. Future research should focus on large-scale field applications, standardization of design methodologies, and the integration of advanced computational modeling for performance optimization. This study contributes to the development of sand–rubber mixtures, positioning them as viable and ecological solutions within the framework of circular economy principles and sustainable construction practices. Full article

This study investigates the behaviour of dense silty sands with kaolinite clay under static drained/undrained conditions at low confining stress. Conventional laboratory tests assessed the mixtures’ physical properties, but standard void ratio methods proved inadequate for silty sands with kaolinite. Despite targeting 80% relative density, specimens exhibited loose sand behaviour in both drained and undrained tests. With increasing kaolinite content, conventionally reconstituted mixtures exhibit reduced peak stress ratios up to 10% fines, with little change beyond, while critical ratios generally rise at 25 kPa but remain unchanged or decrease slightly at 50 kPa. Analytical redefinition of minimum/maximum void ratios (based on sand–clay volumetric fractions) improved specimen reconstitution, yielding dense behaviour matching that of the host sand. The alternatively reconstituted mixtures display increasing drained peaks and minor changes in undrained peaks with increasing kaolinite content, with critical ratios increasing markedly at 25 kPa and only slightly at 50 kPa. However, this analytical void ratio determination method is limited to non-expansive, low-plasticity clays. Void ratios in silty sands with clay mineras are influenced by confining stress, drainage, saturation, clay content, and the sand skeleton structure. Unlike pure sands, these mixtures exhibit variable void ratios due to changes in the clay phase under different saturation levels. A new evaluation method is needed that accounts for clay composition, saturation-dependent consistency, and initial sand skeleton configuration to characterise these soils accurately. The findings highlight the limitations of conventional approaches and stress the need for advanced frameworks to model complex soil behaviour in geotechnical applications. Full article

Accurate prediction of soil–structure interface shear strength (τ_max) is critical for reliable geotechnical design. This study combines experimental testing with interpretable machine learning to overcome the limitations of traditional empirical models and black-box approaches. Ninety large-displacement ring shear tests were performed on five sands and three interface materials (steel, PVC, and stone) under normal stresses of 25–100 kPa. The results showed that particle morphology, quantified by the regularity index (RI), and surface roughness (R_t) are dominant factors. Irregular grains and rougher interfaces mobilised higher τ_max through enhanced interlocking, while smoother particles reduced this benefit. Harder surfaces resisted asperity crushing and maintained higher shear strength, whereas softer materials such as PVC showed localised deformation and lower resistance. These experimental findings formed the basis for a hybrid symbolic regression framework integrating Genetic Programming (GP) with Shapley Additive Explanations (SHAP), Fourier feature augmentation, and physics-informed constraints. Compared with multiple linear regression and other hybrid GP variants, the Physics-Informed Neural Fourier GP (PIN-FGP) model achieved the best performance (R² = 0.9866, RMSE = 2.0 kPa). The outcome is a set of five interpretable and physics-consistent formulas linking measurable soil and interface properties to τ_max. The study provides both new experimental insights and transparent predictive tools, supporting safer and more defensible geotechnical design and analysis. Full article

Currently, Japan’s fishing industry is facing a severe decline in its workforce. As a response, fishing mechanization using small underwater robots is promoted. These robots offer advantages due to their compact size, although their operating time is limited. A major source of this limited operating time is posture stabilization, which requires continuous thruster use and rapidly drains the battery. To reduce power consumption, anchoring the robot to the seabed with anchors is proposed. However, due to neutral buoyancy, the available thrust is limited, making penetration into the seabed difficult and reducing stability. To address this, we focus on composite-shaped anchors and vibration. The anchors combine a conical tip and a cylindrical shaft to achieve both penetrability and holding force. However, a trade-off exists between these functions depending on the tip angle; anchors with larger angles provide better holding capacity but lower penetrability. To overcome this limitation, vibration is applied to reduce soil resistance and facilitate anchor penetration. While vibration is known to aid penetration in saturated soft soils, the effect of tip angle under such conditions remains unclear. This study aims to clarify the optimal tip angle for achieving sufficient penetration and holding performance under vibratory conditions. Experiments in underwater saturated soft soil showed that vibration improves both penetration and holding. This effect was strong in anchors with tip angles optimized for holding force. These findings support the development of energy-efficient anchoring systems for autonomous underwater operations in soft seabed environments. Full article

Accurate evaluation of subgrade behaviour under dynamic loading is essential for the long-term performance of transport infrastructure. While the Light Weight Deflectometer (LWD) is commonly used to assess subgrade stiffness, it provides only a single stiffness value and may not fully capture the time-dependent response of soil. This study presents an image-based vision system developed to monitor soil surface displacements during loading, enabling more detailed analysis of dynamic behaviour. The system incorporates high-speed cameras and MATLAB-based computer vision algorithms to track vertical movement of the plate during impact. Laboratory and field experiments were conducted to evaluate the system’s performance, with results compared directly to those from the LWD. A strong correlation was observed (R² = 0.9901), with differences between the two methods ranging from 0.8% to 13%, confirming the accuracy of the vision-based measurements despite the limited dataset. The findings highlight the system’s potential as a practical and cost-effective tool for enhancing subgrade assessment, particularly in applications requiring improved understanding of ground response under repeated or transient loading. Full article