Stone Columns In Soft Clay Research Articles

Prediction of bearing capacity of geogrid-reinforced sand over stone columns in soft clay

It is a challenge to estimate the ultimate bearing capacity (qrs) of a geogrid-reinforced sandy bed on vertical stone columns in soft clay due to their complex geometry and uncertain parameters. Predicting qrs can be costly and challenging, so creating an accurate prediction model is important for real-world applications. The research aims to use ensemble techniques like K Nearest Neighbors (KNN), Random Forest (RF), and Extreme Gradient Boosting (XGBoost) to develop a model for estimating the bearing capacity of geogrid-reinforced stone columns (GRBS) on a sandy bed with vertical stone columns in soft clay. A dataset of 245 experimental observations is used to train the models. The present study highlights the potential use of the XGBoost model as a useful tool that can assist in predicting the bearing capacity. The results of the study reveal that this model has performed well in predicting the bearing capacity with high correlation coefficients of 0.9947. Furthermore; a SHAP dependency analysis was conducted to ascertain the significance of each parameter.

Vibro stone as periodic wave barriers for train-induced vibration attenuation of Lamb and surface waves

The rising cost of traditional foundations (e.g., concrete piles) and their environmental limits have prompted using natural ways to strengthen poor soils. The Vibro stone column technique has grown in popularity in the building industry because it is a cost-effective and ecologically friendly way of strengthening the soil-bearing capacity of poor soil and avoiding the risk of soil liquefaction. The usage of stone columns in soft clay as periodic wave barriers to attenuate undesirable waves is numerically examined in this paper. The finite element method was used to investigate the band gap characteristics of Lamb and surface waves in the periodic structures of the stone column. In both wave analyses, eigenfrequency simulation, mode shapes simulation, frequency domain simulation, and time transient simulation are used to investigate the traditional vibroflot shape and proposed square and notch types vibroflot. It was established that the notch type vibroflot performed excellently in attenuating Lamb and surface waves compared to the traditional and square vibroflot types. The numerical outcomes in the frequency and time domains support the attenuation impact of finite Vibro stone in the band gap as well as the phenomena of attenuation broadening brought on by the dissipation of leak modes into the bulk. As a result, the proposed barriers can be used to shield the broadband incident waves generated by both Lamb and surface waves by trains in a tunnel.

Developing bearing capacity model for geogrid-reinforced stone columns improved soft clay utilizing MARS-EBS hybrid method

Because of the complicated geometry and a lack of knowledge about the parameters that impact it, estimating the ultimate bearing capacity (qrs) of a geogrid-reinforced sandy bed on vertical stone columns in soft clay is challenging. In practical applications, developing an accurate prediction model can be beneficial due to the difficulty and expense of estimating qrs. The objective of this study is to develop a model for predicting the bearing capacity of geogrid-reinforced stone columns using Multivariate Adaptive Regression Splines (MARS) and Escaping Bird Search optimization algorithm (EBS). In order to accomplish this, 219 constructed experimental samples were used. Feature selection based on the Neighborhood Component Analysis (NCA) method showed that due to the strong correlation between undrained shear strength of unreinforced clay (qu) and the ratio of stone columns distance to foundation diameter (s/D) variables, only qu should be included in the modeling. A developed model for estimating the bearing capacity was found to have coefficients of determination (R2) of 0.997 for training, 0.993 for testing, and 0.995 for total data. This study confirms that the undrained shear strength of unreinforced clay (qu) is the most essential input parameter for assessing bearing capacity, while the the ratio of sandy bed thickness to foundation diameter (t/D) is the least essential input parameter. In addition, the parametric analysis shows that increasing all input parameters increases bearing capacity.

Behaviour of Encased Stone Columns in Soft Clay

Behaviour of Encased Stone Columns in Soft Clay

Behavior of Geosynthetic-Encased Stone Columns in Soft Clay: Numerical and Analytical Evaluations

Behavior of Geosynthetic-Encased Stone Columns in Soft Clay: Numerical and Analytical Evaluations

Influence of Particle Gradation and Shape on the Performance of Stone Columns in Soft Clay

Abstract A stone column typically consists of particles whose influence has largely been overlooked in design practice in terms of stress transfer, pattern of deformation, and intrusion of fines (clogging). This article presents an experimental study on the load-deformation behavior of a model stone column installed in soft clay with a particular emphasis on the influence of particle gradation and shape under undrained loading. The results show that particle gradation and shape have a significant influence on the load-deformation behavior and the extent of fines intrusion into the stone columns. Relatively well-graded particle sizes favor the development of higher peak shear stresses accompanied by lateral bulging, whereas more uniform grading results in the development of distinct shear planes and smaller peak shear stresses. Deformed columns were also examined using computed tomography, and the porosity profiles at the end of the test were determined using micrographs. Maximum porosity typically occurred in the zone of extreme lateral deformation, with the results suggesting that the extent of fines intrusion was influenced by particle morphology.

Performance of Field and Numerical Back-Analysis of Floating Stone Columns in Soft Clay Considering the Influence of Dilatancy

Stone column use has gained popularity around the globe as an effective ground improvement technique to improve the load-bearing capacity of soft soils. End-bearing stone columns are commonly used, but occasionally floating stone columns are adopted since they have been proven to achieve the necessary load-carrying capacity and serviceability requirements. However, stone column parameters are often estimated without much basis for simulation and design purposes due to a lack of practical research and real-life case studies in this area. Hence, in order to develop a fundamental understanding of the load-settlement responses of floating stone columns in soft clays, detailed back-analysis was performed in this study. Throughout the back-analysis, all the numerical models were validated by comparing the analysis results with field measurements. This study highlights the existence of some critical interpreted parameters, namely soil cohesion c′, friction angle ϕ′, and dilation angle ψ′, as well as the soil–structure interaction mechanism that influences the load-settlement responses of the floating stone columns. The successful characterization of the stone column materials and the modeling technique of stone columns in finite element analyses show great potential in assessing the real-life performance of floating stone columns in soft clays.

Bearing capacity of reinforced and unreinforced sand beds over stone columns in soft clay

A series of experiments on the unreinforced sand bed (USB) and geogrid-reinforced sand bed (GRSB) placed over a group of floating stone columns in soft clay and their numerical simulations have been conducted. Three-dimensional numerical simulations were performed using the finite-element package ABAQUS 6.12 for modeling the USB and GRSB placed over a group of stone columns floating in soft clay. In finite-element analysis, geogrid is modeled as an elasto-plastic material. Compared to unreinforced clay, 1.72-fold, 2.83-fold and 5.30-fold increases in bearing capacity can be achieved by the provision of only stone columns, stone columns with USB and GRSB, respectively. The critical thickness of USB and GRSB can be taken as equal to 0.3 times and 0.2 times the diameter of the footing; above this thickness, improvement in the bearing capacity is marginal. Both the improvement factor and stress concentration ratio of the stone columns with GRSB show an increasing trend with an increase in settlement. The optimum length of the group of floating stone columns with GRSB is six times the diameter of the column. Plastic strain developed in the stone column material is much higher than that in the geogrid planar sheet.

Bearing capacity of geogrid reinforced sand over encased stone columns in soft clay

Stone columns develop their load carrying capacity from the circumferential confinement provided by the surrounding soils. In very soft soils, the circumferential confinement offered by the surrounding soft soil may not be sufficient to develop the required load carrying capacity. Hence a vertical confinement would yield a better result. The load carrying capacity is further increased with the addition of a sand bed over the stone columns. In the present study, a series of laboratory model tests on an unreinforced sand bed (USB) and a geogrid-reinforced sand bed (GRSB) placed over a group of vertically encased stone columns (VESC) floating in soft clay and their numerical simulations were conducted. Three-dimensional numerical simulations were performed using a finite element package ABAQUS 6.12. In the finite element analysis, geogrid and geotextile were modeled as an elasto-plastic material. As compared to unreinforced clay bed, an 8.45 fold increase in bearing capacity was observed with the provision of a GRSB over VESC. The optimum thickness of USB and GRSB was found to be 0.2 times and 0.15 times the diameter of the footing. A considerable decrease in bulging of columns was also noticed with the provision of a GRSB over VESC. Both the improvement factor and stress concentration ratio of VESC with GRSB showed an increasing trend with an increase in the settlement. It was observed that the optimum length of stone columns and the optimum depth of encasement of the group of floating VESC with GRSB are 6 times and about 3 times the diameter of the column respectively.

The Effect of Granular Material on Behaviour of Stone Columns in Soft Clay under Embankment

The Effect of Granular Material on Behaviour of Stone Columns in Soft Clay under Embankment

Ground heave induced by installing stone columns in clay soils

Measurements of ground heave induced by installing stone columns in soft clay are presented in this paper. These measurements are likely to provide guidance to practitioners concerned about the possible impact of column construction on adjacent structures and services. Heaved volume, variation in heave with radius and the radial extent of heave were found to follow experience of driven piles. Simplified finite-element analyses have also been performed which indicate that the thin stiff crust typical of soft clay profiles appears to have little influence on heave, whereas soil stiffness variation with depth and column length may be influential.

Improvement of soft clay using installation of geosynthetic-encased stone columns: numerical study

The use of geosynthetic-encased stone columns as a method for soft soil treatment is extensively used to increase the bearing capacity and reduce the settlement of raft foundations and the foundation of structures like embankments. Pre-strain is an effect occurring in the encasement during stone column installation due to the compaction of the stone material. The present study uses the finite element program Plaxis to perform a numerical analysis of the soft clay bed reinforced by geosynthetic-encased stone columns. An idealization is proposed for simulation of installation of geosynthetic-encased stone columns in soft clay based on the unit-cell concept. In the analyses, initially, the validity of the analysis of the single column-reinforced soil in the unit-cell model was performed through comparison with the group columns. Then, by considering a unit-cell model, the finite element analyses were carried out to evaluate the stiffness of the reinforced ground to estimate the settlement. The results of the analyses show that the improved stiffness of the encased stone column is not only due to the confining pressure offered by the geosynthetic after loading, but the initial strain of the geosynthetic that occurred during installation also contributes to the enhancement of the stiffness of the stone column and the reduction of the settlement.

The pressure distribution along stone columns in soft clay under consolidation and foundation loading

The mechanism whereby foundation loading is transmitted through the column has received little attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The model tests were carried out on samples of soft clay, 300 mm in diameter and 400 mm high. The samples were reinforced with fully penetrating stone columns, of three different diameters, made of crushed basalt. Four pressure cells were located along each stone column. The 60 mm diameter footing used in the model was supported on a clay bed reinforced with a stone column and subjected to foundation loading under drained conditions. The results show that the dissipation of excess pore water pressure developed during the initial application of total stresses, when the foundation was subjected to no loading, generated considerable stresses within the column, and that this was directly attributable to the development of negative skin friction. The pressure distributions in the column during foundation loading showed some complex behaviour.

Performance of Stone Columns in Soft Clay: Numerical Evaluation

Stone columns (or granular piles) are increasingly being used for ground improvement. This study investigates the qualitative and quantitative improvement in soft clay by stone columns. Finite element analyses were carried out to evaluate the performance of stone columns in soft clay. A drained analysis was carried out using Mohr–Coulomb’s criterion for soft clay, stones, and sand. The interface elements were used at the interface between the stone column and soft clay. Analyses and calculations were carried out to determine equivalent parameters of soil/columns system. The bearing capacity ratio (BCR) of the soil has been estimated for homogeneous and heterogeneous soil. The results have shown that the values of BCR for homogeneous soil are obviously higher than those for heterogeneous soil.

Modelling vibrated stone columns in soft clay

The vibrated stone column technique is an economical and environmentally friendly process that treats weak ground to enable it to withstand low to moderate loading conditions. The performance of the treated ground depends on various parameters such as the strengths of the in-situ and backfill materials, and the spacing, length and diameter of the columns. In practice, vibrated stone columns are frequently used for settlement control. Studies have shown that columns can fail by bulging, bending, punching or shearing. These failure mechanisms are examined in this paper. The study involved a series of laboratory model tests on a consolidated clay bed. The tests were carried out using two different materials: (a) transparent material with ‘clay like’ properties, and (b) speswhite kaolin. The tests on the transparent material have, probably for the first time, permitted visual examination of deforming granular columns during loading. They have shown that bulging was significant in long columns, whereas punching was prominent in shorter columns. The presence of the columns also greatly improved the load-carrying capacity of the soft clay bed. However, columns longer than about six times their diameter did not lead to further increases in the load-carrying capacity. This suggests that there is an optimum column length for a given arrangement of stone columns beneath a rigid footing.

Modelling vibrated stone columns in soft clay

The vibrated stone column technique is an economical and environmentally friendly process that treats weak ground to enable it to withstand low to moderate loading conditions. The performance of the treated ground depends on various parameters such as the strengths of the in-situ and backfill materials, and the spacing, length and diameter of the columns. In practice, vibrated stone columns are frequently used for settlement control. Studies have shown that columns can fail by bulging, bending, punching or shearing. These failure mechanisms are examined in this paper. The study involved a series of laboratory model tests on a consolidated clay bed. The tests were carried out using two different materials: (a) transparent material with ‘clay like’ properties, and (b) speswhite kaolin. The tests on the transparent material have, probably for the first time, permitted visual examination of deforming granular columns during loading. They have shown that bulging was significant in long columns, whereas punching was prominent in shorter columns. The presence of the columns also greatly improved the load-carrying capacity of the soft clay bed. However, columns longer than about six times their diameter did not lead to further increases in the load-carrying capacity. This suggests that there is an optimum column length for a given arrangement of stone columns beneath a rigid footing.

Small diameter reinforced stone columns in soft clay : De, P K, Ray, S Proc Indian Geotechnical Conference, 1989, Geotechniques of Problematic Soils and Rocks, Visakhapatnam, 14–16 December 1989V1, P91–94. Publ New Delhi: Saria Prakashan, 1989

Small diameter reinforced stone columns in soft clay : De, P K, Ray, S Proc Indian Geotechnical Conference, 1989, Geotechniques of Problematic Soils and Rocks, Visakhapatnam, 14–16 December 1989V1, P91–94. Publ New Delhi: Saria Prakashan, 1989