Geotechnics

Clayey soils are generally characterized with low strength and high plasticity which may affect the stability of the subgrade in road infrastructure and hence encourage research into sustainable stabilization techniques. The objective of this study was to investigate the possibility of using recycled crumb rubber (CR) mixed with biaxial geogrid reinforcement to enhance the engineering performance and interface shear behaviour of problematic clayey soil. The experiments were performed on biaxial geogrid BX1100, waste crumb rubber, clay subgrade soil, type B subbase granular material and other materials. The subgrade soil of clay has been collected from the airport area of Al-Muthanna region, Baghdad. An extensive programme of laboratory tests was conducted on soil mixtures with 5%, 10% and 15% of crumb rubber (CR) and untreated soil to determine the effect of stabilization with crumb rubber. The protocol consisted of Atterberg limits, modified Proctor compaction, California Bearing Ratio (CBR) and large-scale direct shear testing. The results showed that the engineering properties of the clay soil were improved by using CR. Maximum improvement was observed at 15% CR content where CBR increased by 56.6% and plasticity index decreased by 44% over the untreated soil. In addition, the large-scale direct shear tests showed that the interface shear strength increased with increasing CR content under geogrid reinforcement. The calculated interaction coefficients were greater than unity for all the tested mixtures indicating effective bonding and interlocking between the reinforced soil layers. The results indicate that the synergistic effect of CR and geogrid reinforcement could improve the interface behaviour of the weak clay subgrade soils with sustainable reuse of waste tyre rubber. Full article

Slope stability assessment remains a fundamental challenge in geotechnical engineering because of the complex nonlinear interactions among soil properties, slope geometry, and hydraulic conditions, particularly variations in pore-water pressure. This study investigates the reliability of Artificial Neural Network–Multi-Layer Perceptron (ANN–MLP) models for predicting the Factor of Safety (FoS) of homogeneous soil slopes through a systematic comparison of three gradient-based optimization algorithms: Adam, Mini-Batch Gradient Descent (MBGD), and Nesterov Accelerated Gradient (NAG). A database comprising 2014 slope cases, compiled from published studies and numerically generated using Limit Equilibrium Method (LEM) and Finite Element Method (FEM) analyses, was used for model development and k-fold cross-validation. Beyond statistical evaluation, the developed models were validated using two classical dry-slope benchmark frameworks based on the Taylor stability charts and Bishop–Morgenstern stability coefficients, followed by two documented engineering case studies from Hulu Kelang and Pahang, Malaysia, to assess predictive performance under both dry and variable hydraulic conditions. Adam achieved the highest cross-validated predictive accuracy (R² = 0.988; RMSE = 0.212), whereas MBGD demonstrated the closest overall agreement with the reference LEM solutions across the validation cases and under increasing pore-water pressure ratios. NAG generally produced more conservative predictions while exhibiting greater sensitivity to hyperparameter selection. All models successfully reproduced the expected nonlinear reduction in FoS with increasing pore-water pressure, consistent with established geotechnical behaviour. The results demonstrate that optimizer selection significantly influences ANN–MLP prediction behaviour and that properly validated gradient-based ANN models can serve as efficient decision-support tools for rapid slope stability assessment under hydraulic variability. Full article

Microbially Induced Carbonate Precipitation (MICP) and Enzyme-Induced Carbonate Precipitation (EICP) have emerged as promising sustainable alternatives to conventional ground improvement techniques. This paper presents a focused review of Cone Penetration Test (CPT)-based assessment of bio-cemented soils, synthesizing findings from studies spanning laboratory column tests, centrifuge models, and field trials. The review examines how CPT measurements, including tip resistance (q_c), sleeve friction (f_s), and pore pressure response (u), reflect the cementation mechanisms, treatment heterogeneity, soil-type effects, and scale dependency characteristic of MICP and EICP treatments. Key findings indicate that MICP and EICP produce distinct CPT responses: MICP-treated sands generally show stronger cementation-related stiffness signatures and more persistent improvement, whereas EICP-treated soils more commonly exhibit sharper near-surface q_c gains that may be more susceptible to reduction with time. However, long-term field CPT evidence for EICP durability remains limited. CPT interpretation is more uncertain in fine-grained and heterogeneous soils, where low permeability, preferential flow, localized cementation, and penetration-induced disturbance can produce irregular profiles that are difficult to interpret from q_c alone. Fundamental limitations of conventional q_c-based CPT interpretation in bio-cemented ground are identified, including its inability to decouple cementation effects from density, stress state, and environmental variability. Multi-sensor CPT platforms integrating shear-wave velocity probes, acoustic emission monitoring, and geochemical sensors are identified as the most promising pathway toward reliable characterization. Three priority developments are outlined: standardized CPT interpretation protocols with calibrated conversion functions for major soil types, validated multi-sensor platforms deployable under field conditions, and machine-learning tools for spatial treatment quality assessment. This review provides a structured CPT-based synthesis of bio-cemented ground and establishes an interpretive basis for future standardized assessment protocols in geotechnical practice. Full article

Large language models are increasingly used to generate engineering code, but executable output does not establish correctness. This study examines an expert supervised workflow used to develop Python implementations for two analytical geotechnical problems: a prescribed circular slip surface calculation using the simplified Bishop method and a shallow foundation bearing capacity calculation. The workflow comprised problem decomposition, specification of geotechnical constraints, modular code generation, expert diagnosis, prompted correction, visual inspection, and comparison with independently configured reference calculations. The slope example documents implementation choices and failure modes for one prescribed slip surface. The bearing capacity study exercised five test groups and 44 calculations covering homogeneous soil, groundwater, two-layer profiles, horizontal loading, and limiting cases. The development process revealed safety-relevant failure modes, including syntax errors, unstable iterations, incorrect geometric extrapolation, and physically inadmissible failure mechanisms. These errors were not resolved reliably by autonomous model self-correction, but required expert diagnosis, modular testing, and constraint-based prompting. The results show that ChatGPT can support the development of geotechnical calculation tools for bounded analytical verification tasks, but only within a strict human-in-the-loop framework. The findings should be interpreted as a case-specific validation of one model system rather than as evidence for the reliability of large language models in general. Full article

Transparent soil technology (TST) provides a non-intrusive visualization approach for geotechnical model experiments by matching the refractive indices of transparent particles and pore fluids. This review systematically examines recent advances in TST, from material preparation to measurement methods and engineering applications. The preparation of transparent sand and transparent clay, pore-fluid matching, degassing treatment, and mechanical similarity with natural soils are summarized. The development of optical measurement and image analysis methods, including laser slicing, particle image velocimetry, digital image correlation, speckle imaging, and three-dimensional reconstruction, is then discussed to clarify the transition of TST from qualitative observation to quantitative full-field deformation measurement. Bibliometric keyword evolution further indicates that research has shifted from early material feasibility toward engineering-oriented applications and intelligent visualization. Current applications in pile–soil interaction, tunneling, slope instability, seepage, and erosion demonstrate the value of TST for revealing displacement-field evolution, strain localization, seepage-path development, particle migration, and shear-band propagation. Remaining challenges include limited mechanical similarity, optical stability, large-scale applicability, and efficient data processing. Future work should emphasize standardized material systems, high-resolution three-dimensional visualization, multiphysics coupling, and integration with artificial intelligence. Full article

Small-scale excavations with depths of approximately 1 to 3 m are widely conducted for purposes such as the repair of underground pipelines. In confined construction spaces, earth-retaining systems consisting of lightweight sheet-piles with struts and walers are frequently used. However, comprehensive investigations of the influence of ground conditions on member forces have not yet been conducted. Furthermore, since these temporary structures are generally not designed with seismic considerations, they may suffer damage during earthquakes depending on the soil conditions. Accordingly, this study conducted a comprehensive parametric numerical investigation to evaluate how differences in soil type, such as sandy and cohesive soils, and loading conditions during excavation and earthquake loading affect the internal forces in the supporting members. Excavation analyses using PLAXIS 3D confirmed that as the soil strength parameters (cohesion and internal friction angle) decreased, the demand on the supporting members increased and larger internal forces developed. Dynamic analyses using LIQCA 3D revealed complex behavior in which (i) earth pressure acting on the wall generated compressive forces in the struts, (ii) lateral deformation of the excavation face reduced axial forces in the struts, and (iii) when the ground liquefied, it exhibited a vibration-isolation effect, and the vibration components generated in the structural members became smaller. Full article

Rocking foundations reduce seismic force demand through controlled uplift and rotation, but their application remains limited by uncertainty in residual settlement and recentring capacity. Grouting is often employed to reduce these serviceability concerns, yet uncertainty in the geometry of the improvement and seismic demand constrains confident adoption. This paper examines whether strength- and serviceability-related responses of jet-grouted rocking foundations exhibit comparable epistemic uncertainty when motion amplitude and grouting layout are represented by bounded Random Set inputs. A sparse deterministic response database was generated using three-dimensional finite-difference modelling for isolated columns, directional walls, and intersecting walls beneath a 3 × 3 m² foundation supporting a bridge-pier-type structure. The grouting layout was represented by a directional stiffness isotropy index. Motion demand was represented through bounded peak ground acceleration intervals. The deterministic results indicate that walls aligned with the excitation direction provide greater settlement reduction and energy dissipation than isolated columns or perpendicular walls. Variation in the depth of intersecting walls further reveals a trade-off between settlement reduction and recentring capacity. Random Set propagation was then used to construct uncertainty bounds for maximum moment, residual settlement, and recentring ratio. The results show that moment demand is comparatively well constrained, whereas serviceability indicators exhibit wider epistemic uncertainty. Full article

This study investigates marine sand collected from the southeastern coast of China through laboratory calibration chamber model tests under varying relative densities and consolidation stresses. The consolidation characteristics and cone penetration test (CPT) penetration response of soil specimens were examined, and interpretation models relating CPT parameters to soil unit weight, relative density, and shear wave velocity were established. Results show that shear wave velocity increases with relative density, with consolidation exerting a stronger enhancement. Lateral earth pressure exhibits a pronounced distance attenuation effect, with stress differences most prominent near-field and diminishing with distance. Cone tip resistance increases with both relative density and consolidation stress, with consolidation stress exerting a more significant influence on low-density specimens; sleeve friction increases linearly with relative density. The interpretation models achieve good correlations with unit weight (R² = 0.78), normalized cone tip resistance with the square of relative density (R² = 0.72), and shear wave velocity (R² = 0.85), and field validation confirms higher prediction accuracy than conventional empirical formulas for terrigenous sands. The models enable rapid, cost-effective parameter estimation from routine CPT data, though they remain site-specific, being based on nine chamber tests and validated against six field layers from a single site. Full article

To elucidate the active–passive reinforcement mechanisms of rock bolts and the evolution of shear strength in anchored rock joints, this study integrates theoretical analysis, laboratory direct shear tests, and numerical simulations to investigate the deformation and failure characteristics of fully grouted, end-anchored, and prestressed bolted specimens. The results show that bolt reinforcement can be classified into prestress-dominated active action and dislocation-induced passive action. The shear strength curve of anchored rock joints exhibits four distinct stages with increasing shear displacement: initial slip, elasticity, yielding, and softening. Fully grouted bolts fail primarily by tensile–shear fracture, enabling a rapid increase in shear strength at small displacements. In contrast, end-anchored bolts undergo S-shaped bending and form symmetrical plastic hinges on both sides of the joint, sustaining resistance under large displacements albeit with lower peak strength. While the laboratory tests experimentally clarified the distinct failure modes and passive shear resistance mechanisms of fully grouted and end-anchored bolts, the quantitative partitioning between active and passive contributions was derived from a numerically simulated prestressed bolt model. The simulations indicate that for prestressed bolts, the active contribution accounts for approximately 69.6% of the total shear strength enhancement, while the passive contribution is about 30.4%. These findings yield actionable design criteria: end-anchored or yielding bolts are recommended for high-geostress environments or scenarios involving large potential deformations to exploit the large-deformation bearing capacity of passive action; conversely, prestressed bolts should be prioritized where strict control of early-stage deformation is required to maximize active support efficiency. Full article

Regional geotechnical archives contain valuable information for numerical modelling, but they are rarely organised in a form that supports traceable derivation of constitutive input parameters for advanced geotechnical analysis. This study develops a groundwater-corrected workflow for transforming regional borehole and consolidation records into finite element-ready constitutive parameter sets for shallow clayey soils, using Al Qadisiyah Governorate, Iraq, as a case study. The workflow combines data cleaning; treatment of limited missing data; derivation of $\lambda$, $\kappa$, $e_0$; preconsolidation pressure, initial effective vertical stress; overconsolidation ratio; and correction of effective stress using observed groundwater conditions. The derived parameter set captures the compressibility, initial state, and stress history variables commonly required for Modified Cam-Clay-based finite element modelling, providing a practical workflow for parameter derivation from routine regional borehole and consolidation data. The results reveal clear vertical and lateral variability in compressibility, density state, and stress history, indicating that the investigated deposits cannot be represented adequately by a single regional parameter set. Groundwater correction was essential for realistic estimation of effective stress and OCR, particularly given the shallow groundwater table throughout the study area. The processed constitutive input dataset was translated into representative finite element material libraries in both overall and depth-specific forms, while GIS-based maps were developed to support spatial interpretation and location-informed parameter selection. The main contribution is the integrated and traceable conversion of regional borehole records into groundwater-corrected constitutive parameters and practical FE material libraries, rather than the separate application of existing empirical or mapping tools. This study demonstrates that routine borehole archives can be transformed into traceable constitutive resources for finite element modelling of shallow clay deposits, supporting preliminary material assignment, depth depth-specific interpretation, and location-informed parameter selection. Full article

Progressive slope failures in open pit mining are characterized by accelerating deformations that can be monitored and potentially forecast. While current monitoring practice emphasizes velocity-based parameters and the inverse velocity method for failure prediction, the role of acceleration in understanding failure mechanisms and improving early warning systems remains underexplored. This paper presents a conceptual and analytical framework for characterizing acceleration in progressive slope failures. We introduce the concept of slope damage as a cumulative measure of positive accelerations over time, and demonstrate its utility in identifying the Onset of Acceleration (OOA), defined as the critical transition from regressive to progressive failure. We further examine the geotechnical conditions necessary for the inverse velocity method to be valid, proposing that a fully or nearly fully mobilized failure surface is required for sustained acceleration. The conceptual link among rock bridge degradation, fracture network connectivity, and the OOA framework is explored using the Network Connectivity Index (NCI), which is presented as a hypothesis for future numerical investigation and systematic empirical testing. This work contributes to the fundamental understanding of progressive failure mechanisms and provides practical guidance for acceleration-based slope monitoring. Full article

Soil–Structure Interaction (SSI) is known to influence the seismic response of structures; however, its implications for the classification of dual wall–frame systems within the framework of Eurocode 8 remain insufficiently understood. This study investigates how SSI affects not only the global response but also the code-based classification of a reinforced concrete dual wall–frame system. A 9-storey prototype building is analyzed using fixed-base and flexible-base models, considering linear-elastic, nonlinear static (pushover), and nonlinear dynamic (time-history) analyses. As expected, the results show that SSI induces a significant redistribution of seismic forces, reducing the contribution of shear walls and increasing the role of frames. As a consequence, the system classification shifts from wall-equivalent dual to frame-equivalent dual, or even toward frame-dominated behavior under Eurocode 8. A comparison with ASCE/SEI 7-16 reveals that such classification changes are less pronounced due to broader system definition limits. The findings highlight that SSI influences not only structural demand but also key design parameters, including behavior factors and force distribution assumptions. This underscores the need for consistent consideration of SSI effects in both analysis and system classification within seismic design codes. Full article

Reliable construction-phase prediction of hard rock tunnel boring machine (TBM) rate of penetration (ROP) remains difficult because ground–machine interaction changes along the alignment and uniaxial compressive strength (UCS) is often incomplete or delayed at ring scale. This study proposes a construction-phase reliability framework that integrates sequence deep learning, inverse-distance-weighted UCS completion, chronological rolling evaluation, PassRate monitoring, and performance-triggered updating. The framework was developed from a granite-dominated TBM drive in northern Thailand and evaluated under a delayed-UCS information policy. In the Phase-2 forward deployment-style evaluation, the selected gated recurrent unit (GRU) model achieved a root mean square error (RMSE) of 0.1639 m/h, a mean absolute error (MAE) of 0.1186 m/h, and 62.63% within a symmetric ±10% accuracy band over 990 evaluated rings. Direct static application of representative theoretical and empirical models produced substantially lower within-band performance of 11.92–20.71%. One early reliability trigger occurred at Ring 3409, after which UCS updating, retraining, and redeployment restored the monitoring process without further intervention triggers. The results show that construction-phase TBM prediction should be managed as an auditable reliability workflow with explicit information boundaries, rather than as a single static accuracy score. Full article

Piles with continuous helix (referred to herein as “screw pile”) is a new configuration of helical piles. It features a continuous helix spiraling several pitches around a smooth shaft forming a “threaded shaft”. This study investigates the compressive capacity and behavior of helical and screw piles using 3D numerical models calibrated and validated against full-scale field testing. The bearing capacity factor, $N_c$, for helical piles is back-calculated from the numerical results and compared against standard theoretical assumptions to evaluate their accuracy in predicting ultimate capacity. Parametric studies are conducted considering screw piles configuration, including shaft diameter, pitch size, helix diameter, as well as soil strength. The results reveal that shaft resistance accounts for up to 89% of the total capacity. Analysis of load distribution, shear contours, and displacement contours at failure allowed for the identification of different failure modes of soil adjacent to the pile’s threaded shaft: Individual Bearing Mode (IBM), Cylindrical Shear Mode (CSM), and a combined mode. The study identifies specific parametric thresholds for these modes in both sand and clay layers. Furthermore, varying clay strength is found to alter the development of the shear surface, transitioning from localized bearing to continuous shearing along the threaded shaft. Finally, apparent shaft resistance factors, $\alpha$ and $\beta$, are back-calculated to provide practical parameters for evaluating the resistance of threaded shafts in layered soil. Full article

While geotechnical parameter determination is fundamental to foundation engineering, traditional approaches often suffer from data fragmentation and subjective safety assessments. This research introduces an integrated framework that synthesizes multivariable regression with the Effective Random Dimension (ERD) method to bridge the gap between raw laboratory indices and structural design. By analyzing datasets from the stable Suceava Moldavian Platform (68 samples) and the tectonized Subcarpathian Flysch (50 samples), the study demonstrates that granulometric fractions, moisture content, and carbonate content can predict consistency limits with high statistical fidelity, achieving R² = 0.98 for the Liquid Limit at Suceava and R² ≈ 0.90 for the Plasticity Index at Doftana. The novelty of the approach lies in the generation of continuous vertical profiles transformed into code-compliant characteristic values (X_k) via Taylor series linearization and the ERD framework. The derived characteristic interval for the Plasticity Index (58.66–70.15%) quantitatively demonstrates the reduction in hyper-conservative bias compared with discrete sampling. This methodology eliminates subjective judgment and ensures a mathematically rigorous transition to Eurocode 7 and NP 122:2010 standards, optimizing both safety and economic efficiency in variable geological strata. Full article

“Interbedded water in thin coal seams” is characterized by its high degree of concealment and complex hydraulic connections. However, due to the confined space of underground mine tunnels and severe electromagnetic interference from metal structures, traditional geophysical methods struggle to accurately delineate the boundaries of water accumulation, making this a major and challenging water hazard in coal mines. Taking the Qinhua Coal Mine in Xinjiang, China, as the engineering context, this paper investigates the detection of water accumulation in interbedded coal seams within goaf areas using the cross-hole resistivity method. It proposes a cross-hole resistivity tomography scanning approach characterized by “progressive depth penetration and layer-by-layer traversal,” and employs an inversion method based on inequality constraints to obtain relatively detailed and reliable imaging results. Through resistivity imaging analysis, low-resistivity water accumulation anomalies were successfully delineated, and water accumulation dead zones were identified. Based on the detection results, effective drainage was carried out beneath the water-filled zones. Subsequent follow-up surveys confirmed the disappearance of the low-resistivity anomalies, thereby validating the reliability and engineering practicality of the cross-hole resistivity tomography method for precisely detecting water body boundaries under complex geological conditions in coal seams. Full article

Expansive clays exhibit shrink–swell behavior driven by microscale physicochemical interactions that are not fully captured by conventional macroscopic descriptors. This study presents a quantitative framework for evaluating microstructural evolution in expansive clays using Environmental Scanning Electron Microscopy (ESEM) combined with fractal dimension and lacunarity analysis under controlled suction paths. ESEM micrographs were collected along primary drying and secondary wetting paths across multiple magnification scales. Fractal dimension quantifies surface complexity, while lacunarity characterizes pore distribution and clustering. Fractal dimension increases with magnification and suction, reflecting greater exposure of particle surfaces as pore water is removed. Lacunarity decreases with magnification and shows soil-dependent trends with suction, indicating changes in pore heterogeneity. Hysteresis in both metrics reveals irreversible microstructural rearrangement associated with particle aggregation and fluid redistribution. These results demonstrate that fractal dimension and lacunarity provide complementary descriptors of soil fabric and establish a quantitative link between microstructure and suction-driven behavior in expansive clays. Full article

Expansive soils undergo structural changes in response to moisture fluctuations, often governed by suction hysteresis. This study investigates the microstructural evolution of three expansive soils using Environmental Scanning Electron Microscopy (ESEM) under controlled drying and wetting cycles across a broad suction range. Soils were prepared with varying compaction states, equilibration times, and physicochemical properties—including specific surface area (SA) and cation exchange capacity (CEC). Images captured at multiple magnifications revealed key trends in water film behavior, cracking, and fabric rearrangement. Image-derived pore-area ratios were used as comparative indicators of microstructural deformation during drying and wetting. High-activity clays (as defined by SA and CEC) displayed pronounced hysteresis and cracking, while low-activity soils exhibited minimal structural change. These findings highlight the role of microscale behavior in expansive soil performance and provide a foundation for improved predictive modeling. In addition, the study provides a framework for future quantitative microstructural characterization using fractal descriptors, enabling future analyses to capture pore complexity and scale-dependent fabric evolution during suction hysteresis. Full article

The stability of tailings dams is governed predominantly by the physical properties and geotechnical behavior of their primary construction material—tailings. Consequently, a systematic understanding of these characteristics is of great significance for the rational design and long-term stable operation of tailings dams. This review focuses on the physical properties and geotechnical behavior observed in different types of tailings. In terms of physical properties, the particle size distribution exhibits a pronounced hydraulic classification characteristic within the impoundment, consisting predominantly of silt-sized particles and displaying an overall trend toward finer gradation. The mineralogical and chemical composition is dominated by quartz, hematite, and silicates. However, significant spatial variability exists both between different tailings types and across distinct zones within the same tailings pond. Regarding geotechnical behavior, the permeability of tailings is governed by a fines content threshold: below this threshold, permeability decreases with increasing fines content, while beyond it, the permeability stabilizes. When studying consolidation and compression behavior using slurry specimens, the compression curves exhibit nonlinear characteristics, primarily described by the modified Gibson theory. The shear behavior of tailings is significantly influenced by confining pressure, drainage conditions, anisotropy and stress paths. The presence of transitional behavior leads to the critical state line determined based on a single sampling method erroneously assessing the dilation/cosntraction characteristics of in situ tailings, thereby affecting the assessment of liquefaction risk. Future research should focus on the seepage, consolidation and shear properties of clayey fine-grained tailings and unsaturated tailings, and aim to elucidate the key controlling factors of transitional behavior to enhance the reliability of tailings dam stability assessments. Full article