Stone Columns Research Articles

Cyclic response of floating geosynthetic-encased steel slag columns in soft clay

Geosynthetic-encased stone column (GESC) technology for strengthening soft clay offers significant advantages in terms of cost-effectiveness, environmental sustainability, and engineering applicability. It is widely applied in treating soft foundations for railways, bridges, and embankments. This study evaluates the cyclic response of the geosynthetic-encased steel slag column (GESSC) composite foundation employing three-dimensional nonlinear finite element analysis. A numerical study is conducted to assess the cyclic response of floating GESSC considering the influence of key design variables, including cyclic load amplitude, loading frequency, geosynthetic encasement stiffness, and length-to-diameter ratio. Results show that both cyclic load amplitude and frequency affect the cumulative settlement and excess pore pressure within the GESSC foundation. Within specified limits, increasing the encasement stiffness and column length can significantly improve the GESSC load-bearing characteristics. The parametric study suggests an optimal geosynthetic encasement stiffness for the field prototype columns within the range of 4480–5760 kN/m and a critical steel slag column length of 10 times the column diameter.

Numerical Simulation of the Load Transfer Mechanism of a Geosynthetic Encased Stone Column Unit Cell under Embankment Loading

Numerical Simulation of the Load Transfer Mechanism of a Geosynthetic Encased Stone Column Unit Cell under Embankment Loading

Consolidation Behaviour of Stone Columns Made with Tyre-Derived Aggregates

Consolidation Behaviour of Stone Columns Made with Tyre-Derived Aggregates

Shear Strength of Geosynthetic-Encased Stone Columns in Unsaturated Soils

Shear Strength of Geosynthetic-Encased Stone Columns in Unsaturated Soils

Free strain consolidation of soft ground improved by stone columns under time-dependent loading considering smear effects

This paper presents a consolidation model for stone column-reinforced soft ground subjected to time-dependent loading under free strain condition. Smear effects and three types of loadings, namely, constant loading, ramp loading, and sinusoidal loading, are considered in the developed consolidation model, which is solved by a numerical method based on a partial differential equation solver. The applicability of the proposed consolidation model and the reliability of the numerical method are demonstrated and verified by well-predicting the consolidation behaviors of two practical engineering cases and one laboratory experiment. The verified model and the numerical method are then employed to investigate the effects of smear zone and time-dependent loading on consolidation characteristics of stone column-improved soft ground. The results indicate that the excess pore water pressure undergoes a sharp change at the interface between the smear zone and the undisturbed zone due to smear effects. The smaller the range of the smear zone, the faster the settlement of the composite foundation develops. The faster the loading rate, the faster the dissipation of excess pore water pressure and the faster the settlement develops. In addition, for the foundation subjected to sinusoidal loading, the higher loading frequency results in a larger amplitude corresponding to the excess pore water pressure and a smaller amplitude corresponding to the settlement of the soil.

Effect of Column Material Internal Angle of Friction and the Geotextile Stiffness on the Behavior of Group of Geosynthetic-Encased Stone Column

Effect of Column Material Internal Angle of Friction and the Geotextile Stiffness on the Behavior of Group of Geosynthetic-Encased Stone Column

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.

Innovative Approaches to Soft Clay Stabilization: Utilizing Sustainable Materials for the Stone Column Technique

Innovative Approaches to Soft Clay Stabilization: Utilizing Sustainable Materials for the Stone Column Technique

Vibro stone column ground improvement practice in the United Kingdom

Vibro stone-column (VSC) techniques have been applied in the United Kingdom (UK) since the late 1950s–early 1960s, where they are one of the most commonly adopted ground improvement techniques. While there have been significant advances in VSC equipment development and also in the monitoring of the installation process for the VSC technique over the past 50 years, the design of VSC remains largely empirical and has changed very little since the 1970s. Publication of well-documented case histories and of instrumented field trials has also been limited over the past 25 years in the UK, in a VSC ground improvement market, which is predominantly commerce driven, based on the cheapest price. This has inherent implications for further advancement of design and innovation through funded full-scale field-based research. Current state-of-the-art of VSC in UK ground improvement is reviewed in the above context, together with comments on future challenges.

Use of Sustainable Material as Column Filler in Soft Clay Bed Reinforced with Stone Column: Numerical Study

Use of Sustainable Material as Column Filler in Soft Clay Bed Reinforced with Stone Column: Numerical Study

Electrokinetics in a Stone Column Encased by a Conductive Jute Geotextile: The Role of Anode Materials

Electrokinetics in a Stone Column Encased by a Conductive Jute Geotextile: The Role of Anode Materials

A numerical investigation into the equivalent parameters of a compressible soil treated by stone columns

A series of triaxial test simulations are adopted to estimate the equivalent strength parameters for compressible soil samples reinforced with stone columns. The simulations utilize the finite difference code, Fast Lagrangian Analysis of Continua in three dimensions FLAC3D. An elasto-plastic model is applied to utilize a Mohr-Coulomb yield criterion. The equivalent strength parameters are estimated using newly proposed formulas for geo-composite materials. The researchers compare the obtained results to the analytical formulas proposed in the literature. Additionally, the equivalent parameters are used in equivalent area models. This study investigates the effect of the replacement area ratio. This study offers two applications. Firstly, it evaluates the safety factor of embankments constructed on compressible soil improved with stone columns. Secondly, it estimates the bearing capacity of strip footings on compressible soil treated with stone columns. In all applications, both individual column and equivalent area models are considered. The proposed equations for the equivalent elastic parameters (E, ν) and the mechanical properties, equivalent cohesion, and internal frictional angle (c and φ) give results that agree with the solutions reported in the existing literature.

Research on construction parameters of stone columns for liquefaction mitigation in coral reef sand areas

For loose coral reef sand with high fines content located in strong earthquake zones, it is necessary to choose stone columns as a liquefaction mitigation ground improvement method that can consider both drainage and densification functions. Taking the Tibar Bay Port project in East Timor as an example, the bottom-feed technology of vibrating stone columns was developed, and typical coral reef sand sites with different fines contents were selected as trial test areas. Experimental research was performed to study the construction parameters for onshore and offshore stone column processes. Tests showed that the vibratory process control parameters, quality acceptance standards, and control procedures proposed through research meet the anti-liquefaction requirements for both drainage and densification effectiveness. The different construction characteristics of onshore and offshore stone columns were also analyzed. Considering the particularity of underwater stone column construction, the research results can be used for stone columns reinforced grounds similar to coral sand onshore and offshore.

LESSONS LEARNT FROM SOIL IMPROVEMENT CASE STUDIES

In Saudi Arabia two methods of soil improvement have been customarily employed. They are soil improvement by means of stone columns, and soil improvement by means of controlled modulus columns, that is CMC. Each of these methods have their own challenges to offer. Experience has shown that the sub-surface geology of the coastal areas of Saudi Arabia are marked with deep layers of poor soil termed locally as sabkha soil. Test results have determined that sabkha soil is known to have low shear strength, high soil compressibility, and high concentration of chlorides and sulphates which are corrosive to concrete, steel, and other construction materials. Design of foundations over a sabkha deposit remains a challenge and requires soil improvement. The CMC installation utilizes reverse flight augers, which displaces the soil laterally. However, it offers a huge challenge of post-operation trimming and cutting of CMCs. for stone columns, soil is removed during the drilling operation creating environmental issue. It also offers challenges as the huge impact during its operation are likely to damage the underground utilities. The environmental issues thus created can pose yet other challenge. This research paper is a case study that collates the experiences of soil improvement methods employed on a project in Saudi Arabia – vis-à-vis their advantages and the challenges encountered.

LESSONS LEARNT FROM SOIL IMPROVEMENT CASE STUDIES

In Saudi Arabia two methods of soil improvement have been customarily employed. They are soil improvement by means of stone columns, and soil improvement by means of controlled modulus columns, that is CMC. Each of these methods have their own challenges to offer. Experience has shown that the sub-surface geology of the coastal areas of Saudi Arabia are marked with deep layers of poor soil termed locally as sabkha soil. Test results have determined that sabkha soil is known to have low shear strength, high soil compressibility, and high concentration of chlorides and sulphates which are corrosive to concrete, steel, and other construction materials. Design of foundations over a sabkha deposit remains a challenge and requires soil improvement. The CMC installation utilizes reverse flight augers, which displaces the soil laterally. However, it offers a huge challenge of post-operation trimming and cutting of CMCs. for stone columns, soil is removed during the drilling operation creating environmental issue. It also offers challenges as the huge impact during its operation are likely to damage the underground utilities. The environmental issues thus created can pose yet other challenge. This research paper is a case study that collates the experiences of soil improvement methods employed on a project in Saudi Arabia – vis-à-vis their advantages and the challenges encountered.

Numerical simulation of bending characteristics of geosynthetic encased stone column

A numerical model of the cantilever bending structure of a geosynthetic encased stone column (GESC) of length 3 m and diameter 0.3 m was established using Z-Soil. The aim was to analyze the stress distribution and bending characteristics of the GESC under a bending load and to investigate the impact of encasement strength, encasement stiffness, gravel friction angle, and diameter on the bending characteristics of the GESC. The maximum bending moment of the GESC under bending conditions occurs at the anchored end. The dividing line of tensile and compressive stresses on the gravel in the anchored end section after bending failure appears at a radius of 0.5 of the column above the section centerline. The geosynthetic sleeve exhibits good resistance to tensile stress. The dividing line between the tensile and compressive stresses is located at the centerline of the section. The mechanical properties of the encasements and gravel has a significant impact on bending characteristics of the GESC. Increasing the strength of the encasement and friction angle of the gravel may significantly improve the bending capacity of the GESC, whereas an increase in the stiffness of encasement and diameter of the column decreases the bending deformation of the GESC.

Study on the mechanism of stone column pile formation

This study focuses on the construction mechanism of stone column piles at an iron ore base in China. A theoretical model that describes the stone column pile formation process during sinking was proposed. The calculation formula for the air pressure required to open the pile tip valve during the pile formation process was derived according to the physical and mechanical parameters of the stratum, stone material parameters, and relevant dimensions of the pile tip valve. This ensured that the pile diameter satisfied the design requirements by successfully opening the pile tip valve. The required air pressure values for different pile lengths in the field were calculated based on this theoretical model, and they were found to be consistent with the actual field conditions. These results can serve as a reference for engineering projects.

Comparative Study on the Use of Reinforced Concrete Piles and Rock Columns in Weak Foundation Strata in Zambia

All structures require transfer of loads to the competent strata. Where less competent soil strata is encountered, the use of either pile foundations or ground improvement methods is adopted. In Zambia, reinforced concrete pile foundations are the commonly used deep foundations since, to transmit loads to stronger strata by utilizing foundation soil skin friction, end bearing or both, while also guarding against differential settlement. Unfortunately, this has proved to be an expensive construction method and it requires the use of materials processed in high energy consuming industries. Stone columns, among many techniques, are one of the most commonly used soil improvement techniques. Although this ground improvement method is considered to be relatively cheaper than reinforced concrete piles, as it only requires the use of coarse aggregates that are widely available in Zambia, it is yet to be employed in the Zambian construction industry. As such this research aimed at comparing the use of the two construction techniques by using Finite Element Method (FEM) Analysis Software Plaxis V20 (2D and 3D) under similar loading conditions and soil properties (Lusaka West, Zambia). The resulting models and simulations were used for comparison of the various parameters which included axial loading (and lateral bulging for stone columns) for skin friction characteristics of the models. In the case of stone columns, the effects of internal angle of friction, spacing and surcharge settlement behaviour were taken into account to come up with the best performing stone column model. For calibration and validation purposes, a number of physical experiments were modelled and simulated so as to produce models that matched their predecessors as much as possible, then the soil properties were adjusted to match those obtained from a local site in Lusaka West, Zambia. Based on the results, concrete pile foundations were found to endure a larger loading before attaining the ultimate failure as compared to stone columns, but the serviceability loading state of stone columns was quite similar to that of the concrete pile foundation. Hence for structures requiring relatively low serviceability loading state on relatively large ground surface area, stone columns proved to be a reasonable construction alternative for pile foundations.

Considerations for the static and seismic design of pumped storage reservoirs in soft soils and seismic environments

AbstractFor recent hydroelectric pumped storage projects, the construction of embankment dam structures on alluvial deposits consisting of exceptionally soft soil and in areas with high seismicity was required. This contribution shares experiences and challenges from the static and seismic design of embankment dam structures and ground treatment options. Finite element‐based static and seismic analyses using the Hardening Soil Small Strain model (HSS) showed that preconsolidation has clear benefits compared to stone columns for ground improvement purposes. Regardless of general advantages of surface sealing systems for frequent and rapid impoundment level changes, it was found that clay core design options perform very well under seismic loading conditions and even better than surface‐sealed structures. Seismic ground and structure response analyses involving soft soil considering shear strain‐dependent stiffness degradation revealed that deamplification is expected in contrast to the rule‐of‐thumb amplification approaches enshrined in many seismic design guidelines and codes. It was found that this effect increases with seismic magnitudes and that saturation of peak ground acceleration (PGA) takes place. This results in relatively moderate structure excitations even under significant dynamic excitation.

Prediction and optimization of the bearing capacity of strip footing resting on soft soil improved with stone columns using RSM, ANN, and multi-objective GA

Prediction and optimization of the bearing capacity of strip footing resting on soft soil improved with stone columns using RSM, ANN, and multi-objective GA