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Stone-column’s are recently garnered popularity being an effective ground-enhancement technique. This study investigates stone-column’s reinforcement impacts of black cotton soil (BCS) upon consolidation & strength characteristics. The laboratory experiments were performed upon BCS specimens reinforced with three various diameters (50 mm, 75 mm, & 100 mm) of stone-column’s and four slenderness ratios (l/d = 3, 4, 5, and 6). Consolidation characteristics and load-settlement responses of reinforced & unreinforced samples were compared. Results demonstrate how bearing capacity of reinforced soil rises along both column diameter & l/d ratio under end-bearing conditions. Furthermore, key geotechnical parameters which are compressibility coefficient (a v ), void ratio (e), coefficient of consolidation (C v ), volume change index (m v ), & permeability (k) are significantly affected by stone-column geometry. The findings confirm the efficacy of end-bearing stone columns in improving loading-carrying capacity and expediting consolidation in BCS, underscoring their suitability for ground stabilization in expansive soils.

Purpose Sincethe availability of natural aggregates is very sparse, recycled industrial and construction waste provides a sustainable alternative to ground improvement using vibro replacement method. Utilizing recycled building waste caters the requirement for its disposal and offers an effective remedy for the scarcity of natural resources. The aim of this study was to give a sustainable alternative for the natural aggregates as the material for stone column. Materials and methods A good stone column material should be hard, dense, chemically inert and must comply with the size requirement. The utilization of construction debris and spent railway ballast as column material has been the subject of numerous researches. This work focuses on finding the suitability of railway ballast and concrete debris as alternatives for stone column material. A detailed laboratory testing of these materials has been carried to judge their strength requirements as the material for both Ordinary Stone Columns (OSCs) and Geosynthetic Encased Stone Columns (GESCs). The improvement in capacity of both OSCs and GESCs is evaluated by performing California Bearing Ratio (CBR) test in laboratory by creating unit cell stone column models of different recycled aggregates and comparing their load settlement behavior with natural aggregates. Results and discussion Railway ballast, natural aggregates, concrete debris and virgin soil were found to show decreasing order in CBR test results. Loading required for causing settlement in both OSCs and GESCsshowed remarkable increase as compared to that of virgin clay and the maximum load settlement improvement was observed for railway ballast in both the types of stone columns. The CBR values for GESC made from railway ballast, natural aggregates and concrete debris were 54, 49 and 38% respectively. On the other hand, CBR for OSC made from railway ballast, concrete debris and natural aggregates were found to be 25.5, 20.4 and 24% respectively and CBR of virgin clay was found to be just 11%. Conclusion The demonstrated application of sustainable sources in place of natural aggregates provides a crucial pathway for utilizing the recycled aggregates as stone column filler material. Up on encasing the OSC with geotextile the performance of stone columns has improved appreciably in terms of load capacity. Railway ballast and concrete debris can be adopted as an alternate for the natural stone column materials to improve the bearing capacity of site consisting mainly of soft clays.

This paper presents the results of large shaking table tests to investigate the improvement effects of using ordinary stone columns (OSCs), geosynthetic-encased stone columns (GESCs), and surrounded stone columns with filtering material (FSCs) on saturated sand. The internal dimensions of rigid box were 2.35 m and 0.9 m in plan and was filled with 1.1 m Firuzkuh sand using the water pluviation method. The diameters of stone columns (SCs) were 120 mm and 170 mm and the SCs spacing was 300 mm. The embedded lengths of SCs were 1100 mm. The results indicate that, although the increase in excess pore water pressure is not restrained by using OSCs, the use of both GESCs and FSCs are more effective to mitigate liquefaction potential. This is because of the effectiveness of the geotextile and sand filter on preventing the clogging of SCs and allowing permanent drainage of SCs during shaking. It was found that in the cases of unimproved sandy ground and improved sand by OSCs at 0.05 g loading horizontal acceleration, sand became totally liquefied, while in the cases of improved sand by GESCs or FSCs, under approximately 0.2 g acceleration, the soil close to the SCs was not liquefied.

Geosynthetic-encased stone columns (GESCs) effectively improve soft soils where traditional stone columns lack sufficient lateral confinement. The complex interaction among the column, encasement, and surrounding soil necessitates an analytical model for efficient prediction and design. This study presents a simplified semi-analytical iterative solution to evaluate ground reinforced with GESCs. The system is modeled as a unit cell with regularly arranged end-bearing stone columns in soft soil. The stone column is idealized as a rigid-plastic material, yielding at active stress and deforming plastically without volume change, while the geosynthetic encasement is represented as linear-elastic, and the surrounding soil is modeled using semi-empirical assumptions in which horizontal stresses are linearly proportional to vertical stresses. The soil profile is divided into horizontal slices to account for depth-dependent behavior, applicable to both homogeneous and layered soils, and to un-encased, partially encased, or fully encased columns. Validation with field tests and finite element analysis shows that the proposed solution provides comparable results for settlements, stress distribution in both soil and stone columns, and encasement radial expansion. The model is effective across a wide range of area replacement ratios (i.e., 0 to 0.35) and encasement stiffnesses (0 to 5000 kN/m), with optimal stiffness effects calculated between 2000 and 3000 kN/m. Parametric analyses reveal that settlement improvement and stress concentration are most sensitive to the area replacement ratio, encasement stiffness, and soil stiffness, while increasing column diameter beyond an optimal value reduces effectiveness. An optimum partial encasement length ratio of 0.45 was identified, beyond which the Settlement improvement factor (SIF) increases only marginally. The proposed model also provides an analytical design chart for evaluating the settlement of GESC-reinforced soft soils, along with a Python-based code for calculation.

Stone columns are widely used around the world as a cost-effective soil improvement technique for highways and embankments. They are also used as drainage to expedite the consolidation period of soft clay, and accordingly to increase the shear strength, to reduce settlement and liquefaction potential. Currently the design of these columns is based on the unit cell or homogenized material concept, which overlook the effect of the interaction of columns within the group. A prototype experimental setup was developed to simulate the case of soft clay reinforced with a group of stone columns. The setup consisted of a triaxial facility, consolidation tank, hydraulic loading system and reaction loading frame. The test commenced by filling the consolidation tank with the laboratory prepared clay. At the end of the consolidation process a group of stone columns was installed into the clay. Blocks of a stone column together with the surrounding clay were extracted from the consolidation tank for testing in the triaxial chamber. The results support the existance of column’s interaction and a group of stone columns may fail by general or local shear, while a single column may fail by bulging. Furthermore, the level of improvement increases with the increase of the replacement area, while spacing and diameter of columns have little effect on the level of improvement. An improvement factor was introduced as “IMF”.

The use of stone columns as a ground improvement technique in landfill sites has gained significant attention due to their potential to enhance stability, reduce settlement, and facilitate efficient drainage within the clay barrier layer. This study examines the performance of stone columns placed beneath a clay barrier in a controlled landfill environment. A laboratory-based physical experiment was conducted using two lysimeters filled with organic waste to simulate landfill conditions, with continuous monitoring over 5 months. This research specifically aims to evaluate the effectiveness of stone columns in controlling settlement, optimizing drainage, and preserving liner integrity under waste accumulation and structural loading. The experimental setup involved the installation of 2.5 cm diameter stone columns at a spacing of 7.5 cm (3D), with a length-to-diameter ratio (L/D) of 8 key parameters—including moisture content, temperature, liner pressure, total dissolved solids (TDS), pH, and settlement—were systematically recorded using embedded sensors. Additionally, a structural load was applied to assess its influence on the soil mass beneath the barrier. The findings indicate that stone columns significantly enhance landfill stability by improving drainage efficiency, maintaining consistent pressure, regulating temperature variations, reducing settlement, minimizing TDS accumulation, and stabilizing pH levels. These results underscore the viability of stone columns as an effective long-term solution for improving the performance and containment efficiency of landfill liners.

Three different liquefaction mitigation techniques for an earthen embankment resting on saturated loose cohesionless soil have been compared in the present study as densification of foundation soil, stone column mitigation, and hybrid pile-stone column mitigation. Numerical modelling has been done using finite element modelling assuming plane strain condition. Liquefaction behaviour of the foundation soil has been modelled using the effective stress-based elasto-plastic UBC3D-PLM model. All the three mitigation models along with the benchmark model have been analysed under 25 different real ground motions. The maximum embankment crest settlement has been occurred in the Imperial Valley (1979) ground motion having the maximum Arias Intensity. The maximum crest settlement and the maximum excess pore pressure ratio in the mitigation zone below embankment toe found to be increasing with Arias Intensity of ground motions. In case of mitigation using densification of region below the embankment toe, the mitigated zone away from the toe towards the free field liquefies. The stone column mitigation reduces the excess pore pressure more efficiently beneath the embankment toe region than other two mitigation techniques. The hybrid mitigation with a combination of gravel drainage and pile found to be more effective to reduce the excess pore pressure as well as the shear-induced and post-shaking settlement due to the rapid dissipation of excess pore pressure of the foundation soil.

Many coastal areas have soft clay soils, characterized by high compressibility and low bearing capacity. There are several methods for improving soil characteristics, one of which is stone columns technique. This method can reduce the possibility for liquefaction, speed the consolidation effect, strengthen the soil, and lessen the compressibility of soft, loose, and fine-graded soils. In this study, unit cell stone columns with 50- and 75-mm diameters and the length of stone column to the depth of the soft clay (L/H) of 1 and 0.75, were subjected to laboratory experiments on soft clay soil with a cohesion of 7 kPa. Crushed asphalt, crushed concrete, crushed ceramic, dolomite, and treated concrete were tested as filler materials in the stone columns. In addition, tests were conducted on both unreinforced and geogrid-encased stone columns. The main objective is to identify the most effective filler material that improves in load-bearing capacity and minimizes the settlement. The behavior of stone columns was assessed by varying stress concentration ratio (n) and the load improvement factor (LIF). The results indicate that both n and LIF increase with increasing the settlement to the plate diameter ratio, reaching a stable value when that ratio reaches 10% or higher. Consequently, it can be inferred that using floating stone columns is more economically efficient than using end-bearing stone columns. Increasing the length and reinforcing the vertically encased stone columns improve both the bearing capacity and the stress concentration ratio. All the materials used in this study improved the bearing capacity and reduced settlement. It is observed that treated concrete yielded the best results in improvement, while crushed asphalt is considered the most economical option compared to the other materials used.

Stone columns are widely used as a cost-effective solution for enhancing the engineering behaviour of weak soils. Granular materials such as natural aggregates, which have higher stiffness than native soil, are used as the backfilling materials in the vertical boreholes in the ground, which results in improving the load-bearing capacity of existing weak soil. However, the growing utilisation and greed for extreme usage of natural aggregate poses challenges such as resource depletion, increased carbon emissions and ecological disruption, rendering it unsustainable. As a result, it is critical to create a sustainable substitute for natural aggregates in the construction of stone columns. Thus, nowadays, waste materials are widely used to tackle the problem of resource depletion, which indeed helps conserve resources and mitigate the effects of climate change. This paper presents a review of various literature available on the use of waste materials as a replacement for natural aggregate in stone column construction. The paper includes different types of soil that have been stabilised using waste materials, installation methods employed, experimental work and, most importantly, the outcomes derived from the utilisation of waste materials. The primary conclusion obtained from the current study is that some waste materials, like silica manganese slag, concrete waste, tyre waste, etc., are proven to be more effective when used in correct proportions. It has also been observed that using waste materials offers a sustainable and highly effective approach, particularly considering the conservation of natural resources. The study also presents several recommendations pertaining to the future scope.

The equivalent shear strength of the composite soil reinforced by stone columns was studied using an FDM-DEM numerical method. In the numerical model of composite soil, the stone column was represented by discrete rigid blocks based on the Voronoi tessellation, and the continuum Mohr–Coulomb material represented the surrounding clay. The numerical simulation results show that the embedded stone column mainly controls the development of a macroscopic shear slip surface in the composite soil. The interaction between the stone column and the soil portion inside composite soil has been well captured numerically. The numerical simulation results can be used to better understand the failure process of the composite soil reinforced by stone columns. The differences in the equivalent shear strength properties between those calculated using numerical simulation and those predicted by the commonly used analytical formulas have been discussed in this article.