Three-dimensional numerical models are developed to investigate the anti-liquefaction of ordinary (OSCs) and geosynthetic-encased (GESCs) stone columns in sandy soil under sinusoidal loading using the fluid-solid coupling method. The validated models capture and compare the vertical and radial deformation, excess pore water pressure (EPWP), and vertical effective stress of OSC, GESC, and sandy soil. Furthermore, ten essential factors are selected to conduct the parametric study. Numerical results reveal that GESC is more suitable for improving sandy soil and resisting dynamic load considering the deformation and EPWP. The bulging deformation is no longer the primary reason for failure. The partial encasement (e.g., 1-2D, D = column diameter) and short floating and end-bearing GESCs (e.g., 1-2.5D) are not recommended for reinforcing the sandy soil. GESC is more sensitive to low-frequency and high-amplitude loads, with shear and bending, whereas displays a block movement under higher frequency and lower amplitude loading. The change in loading amplitude is more disadvantageous to GESC than loading frequency. GESC with a large diameter cannot effectively resist the dynamic loads.

Stone columns are a resultful measure to increase the bearing capacity of soft or liquefiable foundations. The centrifuge model test and finite element method were employed to investigate the bearing capacity and deformation behavior of the stone column-reinforced foundation. Study shows that the modulus of the reinforced foundation exhibits significant anisotropy. A bulging deformation area is identified in the reinforced foundation where obvious horizontal deformation of the stone column occurs. The ratio of the column stress and soil stress is observed to change violently in this area. A homogenization technique is consequently deduced by employing the column-soil stress ratio as a key variable. The definition of the column-soil stress ratio is extended to reasonably describe the column-soil interaction under different stress levels and its approximation method is given. Based on the Duncan- Chang E-nu model, a simplified method using the homogenization technique is proposed for the stone column reinforced foundation. The proposed homogenization technique and simplified method have been validated by the centrifuge model tests and finite element analyses. This method properly addresses the nonlinear spatial characteristic of deformation and the anisotropy of the stone column reinforced foundation.

After sand liquefaction, buried underground structures may float, leading to structural damage. Therefore, implementing effective reinforcement measures to control sand liquefaction and soil deformation is crucial. Stone columns are widely used to reinforce liquefiable sites, enhancing their resistance to liquefaction. In this study, we investigated the mitigation effect of stone columns on the uplift of a shield tunnel induced by soil liquefaction using a high-fidelity numerical method. The liquefiable sand was modeled using a plastic model for large postliquefaction shear deformation of sand (CycLiq). A dynamic centrifuge model test on stone column-improved liquefiable ground was simulated using this model. The results demonstrate that the constitutive model and analysis method effectively reproduce the liquefaction behavior of stone column-reinforced ground under seismic loading, accurately reflecting the time histories of excess pore pressure ratio and acceleration. Subsequently, numerical simulations were employed to analyze the liquefaction resistance of saturated sand strata and the response of a shield tunnel before and after reinforcement with stone columns. Additionally, the effects of densification and drainage of the stone columns were separately studied. The results show that, after installing stone columns, the excess pore pressure ratio at each measurement point significantly decreased, eliminating liquefaction and mitigating the uplift of the tunnel. The drainage effect of the stone columns emerged as the primary mechanism for dissipating excess pore pressure and reducing tunnel uplift. Furthermore, the densification effect of stone columns effectively reduces soil settlement, particularly pronounced around the stone columns, i.e., at a distance of three times the diameter of the stone column.

Geosynthetic-encased stone columns (GESCs) represent an efficient and cost-effective solution for enhancing weak soil foundations. The deformation and load-bearing mechanisms of GESC-improved foundations under traffic flow are complicated due to substantial particle movements and soil disruption. A three-dimensional discrete-continuum coupled numerical model was proposed in this study to investigate the cyclic behavior of GESC-improved soft soil. The reliability and accuracy of proposed model was validated through experimental data. The effect of cyclic loads, bearing stratum, and geogrid encasement was investigated. Microscopic investigation of particle movement, contact force distribution, and stress transfer mechanism was performed. The vertical loads transferred from the column to the surrounding soil with the interaction effect between the aggregates and the soil. The stress concentration ratio decreased with the increase in depth. The geogrid encasement facilitated the load transfer process by effectively confining the particles and enhancing the column stiffness. The particles in the low segment of floating column exhibited large downward displacements and punching deformation. The geogrid encasement and cyclic loads contributed to enhanced compaction and coordination number of the aggregates.

With the growing need for efficient mitigation strategies in liquefaction-prone regions, ensuring both seismic resilience and sustainability of infrastructure has become increasingly significant. This paper presents a datadriven probabilistic seismic demand model (PSDM) prediction and sustainability optimization framework to mitigate liquefaction-induced lateral deformation in regional mildly sloping ground improved with stone columns. The framework integrates finite element (FE) simulations with machine learning (ML) models, generating 1,200 ground FE models based on the key site attributes, such as ground inclination, soil properties, and stone column configurations. The performance of the selected ML models is evaluated through hyperparameter tuning by k-fold cross-validation, with the artificial neural network (ANN) outperforming other models in accurately predicting the PSDM. Subsequently, this framework is applied to a set of representative mildly sloping ground sites, enabling rapid PSDM prediction for each site with varying site attributes. Moreover, by incorporating cost and sustainability metrics, multi-objective optimization is performed using the developed ANN predictive model to maximize seismic performance while minimizing total carbon emissions and costs associated with ground improvement. Overall, the framework allows for rapid and accurate PSDM prediction and regional optimization, facilitating the identification of the optimal stone column configurations for efficient and sustainable liquefaction mitigation.

Cinder gravel, a porous, lightweight, and durable volcanic byproduct, has the potential to be a sustainable and cost-effective alternative to conventional stone columns for ground improvement applications. Its use in soft soils, however, requires sufficient confining pressure to prevent bulging and thus performance degradation. Geotextile-encased cinder gravel (GECG) columns are therefore an innovate method to overcome this, however their bearing response and pressure-deformation characteristics have received limited study. This paper presents a comprehensive numerical analysis for GECG columns using a coupled discrete element and finite difference method (DEM-FDM). The hybrid DEM-FDM framework enables the simulation of individual particle behavior while maintaining efficiency in modeling continuous, homogeneous materials. The key novelties are examining the macro and mesoscopic behavior of GECG columns under triaxial compression. To do so, the development of the numerical model is introduced, followed by its validation and calibration against triaxial test results. Subsequently, a parametric analysis of GECG columns investigates the influence of relative density and gradation on the compression behavior and load capacity. Upon triaxial compression, the findings reveal a significant radial expansion near the column top, with stress and deformation fields aligning with the column's bearing capacity. The relative density exerts limited influence on the geotextile's radial deformation, and the higher content of coarse particles in the gradation enhanced the bearing capacity of the GECG columns.

Soil reinforcement is one of the techniques used to enhance the engineer characteristics of the soil. Various techniques can be employed to stabilise problematic soils, such as soft clay. These include the utilisation of portland cement, lime, fly ash, ground freezing, jet grouting, prefabricated vertical drains, and thermal approaches. Similarly, stone columns are one of the most popular methods for enhancing soil and have been adopted across the world to enhance bearing capacity and minimise total and differential settlements of structures built on soft clay. Additionally stone columns serving as vertical drains, thus accelerate consolidation process. But with higher demand of construction material and depletion of natural resources, there is a need of using waste products as a substitute to existing construction materials. In this paper, manufacturing waste like steel slag is used as a sustainable material for column infill and can be affordable and also address the current environmental concern which by removing solid waste & mldr; A series of numerical investigation was carried out to study the various behavioural characteristics of virgin soft clay bed, clay bed installed with ordinary steel slag column and also with encased steel slag column. A comparison was made among all for studying the various parameters such as settlement, excess pore water pressure, stress concentration ratio & lateral deformation of columns.

When stone columns or vertical drains are applied to improve soils, it is common to face situations where the soft soil layer is too thick to be penetrated completely. Although consolidation theories for soils with partially penetrated vertical drains or stone columns are comprehensive, consolidation theories for impenetrable composite foundations containing both two types of drainage bodies have been few reported in the existing literature. Equations governing the consolidation of the reinforced zone and unreinforced zone are established, respectively. Analytical solutions for consolidation of such composite foundations are obtained under permeable top with impermeable bottom (PTIB) and permeable top with permeable bottom (PTPB), respectively. The correctness of proposed solutions is verified by comparing them with existing solutions and finite element analyses. Then, extensive calculations are performed to analyze the consolidation behaviors at different penetration rates, including the total average consolidation degree defined by strain or stress and the distribution of the average excess pore water pressure (EPWP) along the depth. The results show that the total average consolidation rate increases as the penetration rate increases; for some composite foundations with a low penetration rate, the consolidation of the unreinforced zone cannot be ignored. Finally, according to the geological parameters provided by an actual project, the obtained solution is used to calculate the settlement, and the results obtained by the proposed solution are in reasonable agreement with the measured data.

This study investigated the consolidation behavior of silty sand improved with stone columns using a laboratory model based on the unit cell concept. The research focused on analyzing settlement, total stresses, and pore water pressures. Quantitative results showed that increasing the area replacement ratio and relative density reduced settlement, stress distribution, and pore pressure dissipation. The settlement reduction ratio increased with higher area replacement ratios, showing values of 1.12, 1.38, and 1.73 for ratios of 0.03, 0.06, and 0.11 at 40% density and values of 1.23, 1.48, and 2.18 at 90% density. Stress on the stone column increased by 3.7 to 5.0 times for 40% density and 3.0 to 4.2 times for 90% density compared to unimproved soil. Stone columns improved load-bearing capacity and accelerated consolidation by reducing pore water dissipation paths. Column efficacy increased with higher area replacement ratios and relative density, indicating effective stress transfer. Analytical comparisons showed that consolidation in model tests occurred faster than predicted by the Terzaghi and Barron methods, with results of the Carillo method aligning closely with laboratory tests. The study confirmed that stone columns significantly enhanced the consolidation behavior and stability of silty sand.

This paper presents a comprehensive case study on the numerical analysis of stone columns as a ground improvement technique for an expressway embankment. The primary objective is to assess the effectiveness of stone columns in enhancing the performance of predominantly fine-grained soils using Finite Element Method (FEM) analysis. To achieve the objective, detailed numerical models are developed in both three-dimensional (3D) and two-dimensional (2D) plane strain configurations to simulate embankment conditions accurately. Key geotechnical parameters, including the modulus of elasticity and hydraulic conductivity of the stone column material, are incorporated to account for the improved stiffness and drainage effects. The installation process considers critical factors such as vibration-induced changes and horizontal displacement to capture the evolution of soil stress conditions. A staged construction approach is implemented to realistically simulate the sequential embankment construction process and its impact over time. To ensure model reliability, validation is performed by comparing numerical results with field measurements obtained from horizontal inclinometers installed beneath the embankment. The analysis focuses on key performance indicators such as settlement behaviour, the generation and dissipation of excess pore water pressure, and overall stability assessments. The results demonstrate a strong correlation between numerical predictions and field observations, confirming the accuracy of the developed models. This study provides valuable insights into the performance of stone column-reinforced embankments, highlighting significant improvements in load-bearing capacity, reduction in settlement, and overall ground stability. By evaluating the role of stone columns in accelerating consolidation and enhancing the stiffness, strength, and stability of fine-grained soil layers, the research contributes to the optimisation of design and construction methodologies for ground improvement. Additionally, a comparative assessment of 3D and 2D plane strain numerical models is conducted to evaluate their predictive capabilities in representing real embankment behaviour. The findings support the advancement of safer and more resilient infrastructure solutions.