Single Stone Column Research Articles

A Study of Single Stone Column Bearing Capacity from a Full-Scale Plate Load Test in Long Son Project

A Study of Single Stone Column Bearing Capacity from a Full-Scale Plate Load Test in Long Son Project

The Effect of Scrap Tires and Reclaimed Asphalt Pavement on the Behavior of Stone Columns

The objective of this investigation is to understand how to use waste tires to surround stone pillars and mix gravel with recycled asphalt pavement (RAP) and stone pillars to provide an environmentally friendly and cost-effective weak layer improvement method. To study the behavior of such stone columns, experiments were conducted in units consisting of a single stone column with recycled asphalt pavement as filling material and a single stone column covered with old tires. To test the effect of different mixing ratios, rapeseed content was selected from 0% to 100%. Elasticity tests were conducted on cladded and nonclad stone column samples. Furthermore, direct shear tests were conducted on samples with different ratios of gravel and rapeseed mixtures. The results of the load-bearing capacity test show that the cover of the stone columns with old tires can significantly increase the load-bearing capacity. Replacing 25% of natural stone column aggregates with RAP increases the load capacity. But as the percentage of RAP in the mixture increases from 25% to 100%, the loading capacity decreases. Another advantage is the reinforced stone column. From the point of view of ecology, an advantage is the use of recyclable materials.

Experimental studies on use of bamboo mat as stone column encasement in clayey soils

With the rapid urbanization and industrialization; scarcity of useful land is experienced for the infrastructure projects particularly in the urban areas. This has resulted in the use of sites with weak soil deposits such as soft clayey soils. Numerous problems are associated with these soils are high volumetric changes, heave, low bearing capacity, etc. So as to minimize the constructional difficulties associated with the soils; ground improvement techniques are practiced quite frequently on the sites. Stone column provision is one such approach used widely in the fields to enhance the properties of the weak soils. The stone column installation involves partial replacement of 10–35% of weak soils by gravelly materials to form stiffer composite mass.In the present study, an experimental program was undertaken to observe the improvement in strength properties of soft clayey soils collected from Nagpur area, Maharashtra State, India on insertion of stone column. Stone columns were placed single and in group with triangular arrangement. Effects of varying length (L) to diameter (D) ratios (i.e. L / D ratio) of stone columns on the strength properties were analyzed.As an attempt towards sustainable construction; demolition aggregates was used as partial replacement to the natural aggregate while preparing the stone columns. To increase the stiffness of stone column, cement was attempted in small quantity (4% by weight of aggregate) while preparing the specimen. Further, the use of bamboo mat as encasement was planned to study further improvement in load carrying capacity of stone column by increased lateral confinement.The experimental observations depict overall improvement in the load carrying capacity of clay beds on insertion of stone columns. Laboratory testing confirms the possibility of use of demolition waste in stone column construction, as the observed strength (uni-axial compressive strength) is 60–75% of the natural aggregate stone column. Use of bamboo as encasement is effective and shows noticeable improvement in the load carrying capacities (nearly 35–60%) and reduced settlement. Further, study illustrate that the use of single stone column is more effective.

Experimental Study of Bearing Capacity in Single and Group Stone Columns With and Without Encasement

Experimental Study of Bearing Capacity in Single and Group Stone Columns With and Without Encasement

The Effect of Using Reinforced Granular Blanket and Single Stone Column on Improvement of Sandy Soil: Experimental Study

The Effect of Using Reinforced Granular Blanket and Single Stone Column on Improvement of Sandy Soil: Experimental Study

Utilization of Shredded Waste Tire as a Substitute for Gravel in Stone Column Groups

The present study investigates the load-carrying capacity response of gravel-shredded tire stone column groups as a strategy for strength improvement in loose soils. The experimental study was conducted using large-scale oedometer tests on the stone column groups of gravel and gravel-shredded tire mixtures of different tire content, arrays, and spacings. Also, the efficacy of shredded tire addition on the stone column group bearing behavior was explored using the unit cell concept. To this aim, the entire area of the unit cell was loaded to determine the stiffness of the improved bed soil while applying load directly on single stone columns was done to evaluate the load-carrying capacity of the reinforcing elements. The results demonstrate enhancements in the load-settlement behavior of the stone column groups in mixtures containing 20% of the shredded tire, while further tire addition can adversely affect it. Additionally, adding an optimum shredded tire to the stone column materials leads to an increase in stiffness (Young's Modulus) of the bed soil. This behavior is directly correlated with the created friction angle and area ratio (A/AS) of different arrangements of the stone column groups.

Performance of Stone Column in Soft Clay- Numerical Evaluation

Stone columns are an efficient ground improvement technique for treating problematic soils. The confidence in the prediction accuracy of bearing capacity remains unsatisfactory. Soil samples were collected from vellayani paddy field and basic laboratory experiments were done. This paper aims to investigate the bearing capacity of single stone column using three-dimensional numerical analysis. Failure modes were observed and the effect of key parameters such as column’s friction angle, undrained shear strength of surrounding soil and modular ratio were investigated. Numerical results showed bulging and a combination of bulging and punching are two dominant failure modes for the single stone column. Ultimate bearing capacity is mainly influenced by the column’s friction angle and the undrained shear strength of the surrounding soil. Based on the results, a new prediction method is developed and compared reasonably well with the existing analytical solution and the field measurements.

Bearing capacity of single stone column in clay using finite element limit analysis

Stone columns are used as an efficient ground improvement technique, which could increase the bearing capacity of native soft soil, reduce settlement, increase rate of consolidation and mitigate liquefaction potential. In this study, the finite element limit analysis (FELA) with the adaptive mesh, including both upper bound and lower bound approaches, was applied for prediction of ultimate bearing capacity of single stone column. It was observed that a critical slenderness ratio exists in which the failure mechanism changes from punching to bulging. An equation was derived for prediction of the critical slenderness ratio as a function of cohesion of the native clayey soil and friction angle of the stone column. A two-criteria equation is also presented to predict the ultimate bearing capacity of single stone column under both punching and bulging mechanisms. Moreover, the effect of footing roughness on the ultimate bearing capacity of the stone column was investigated. It was observed that the influence of footing roughness is more significant for bulging-type failure. The results of this study are also compared with some of the previously published analyses in the literature.

ESTIMATING LIQUEFACTION RESISTANCE IMPROVEMENT DUE TO STONE COLUMNS FROM QUALITY CONTROL TESTS

Stone columns are often used in cohesionless soils to decrease their liquefaction susceptibility; however, methods of predicting how much liquefaction resistance increases due to stone columnsgreatly vary. All these methods depend on knowing the stone column stiffness but the quality control tests in the field do not lead to measuring actual column stiffness directly, especially the popular plate load tests on a single stone column. A series of axisymmetric numerical simulations of stone column compression investigate the relationship between the actual stone column stiffness and that interpreted from test results. The paper also presents the results of plane-strain numerical models simulating a reference earthquake acting on a unit cell improved by a stone column. The dynamic analysis assesses the change in liquefaction resistance with increasing column stiffness and friction angle. The analysis results show that the PM4Sand dynamic constitutive model is more suitable than the UBC3D-PLM model in capturing the sensitivity of liquefaction resistance to soil improvement and stone column stiffness. The degrees of improvement in liquefaction resistance predicted in the study agree well with what the theories based on combined shear and flexural stone column deformation mechanisms predict. Finally, the paper presents design curves to get a quick estimate of the degree of improvement in liquefaction resistance from plate load test results.

Influence of positions of the geotextile on the load-settlement behaviour of circular footing resting on single stone column by 2D Plaxis software

Purpose: This study aims to study the load – settlement behaviour of circular footing rested on encased single stone column. Design/methodology/approach: The effect of vertical, horizontal and combined verticalhorizontal encasement of stone column on the load carrying capacity were examined numerically. The effect of stone column dimension (80 mm and 100 mm), length (400 mm and 500 mm), and spacing of reinforcement on the load carrying capacity and reinforcement ratio were assessed. Findings: The obtained results revealed that the load carrying capacity of geotextile encased stone columns are more than ordinary stone columns. For vertically encased stone columns as the diameter increases, the advantage of encasement decreases. Whereas, for horizontally encased stone column and combined vertical- horizontal encased stone column, the performance of encasement intensifies as the diameter of stone column increases. The improvement in the load carrying capacity of clay bed reinforced with combined verticalhorizontal encased stone columns are higher than vertical encased stone columns or horizontal encased stone column. The maximum performance of encasement was observed for VHESC1 of D = 80 mm. Research limitations/implications: For this study, the diameter of footing and stone column was kept same. The interface strength factor between stone column and clay bed was not considered. Practical implications: The encased stone column could be use improve the laod bearing capacity of weak soils. Originality/value: Many studies are available in literature regarding use of geosynthetic as vertical encasement and horizontal encasement of stone column. The study on combined effect of vertical and horizontal encasement of stone column on load carrying capacity of weak soil is very minimal. Keeping this in view, the present work was carried out.

Performance of loose sand with different waste materials in stone columns in North Cyprus

Stone columns are used to enhance the bearing capacity of poor ground and reduce the compressibility of soft clays. The aim of this study is to evaluate the effectiveness of stone columns with different waste materials on the performance of loose sand in North Cyprus. The study provides guidelines for the selection of the most effective and economical material for stone column construction. In this study, waste materials from different construction sites were selected: shredded bricks, crushed waste stone and crushed old concrete. The stone columns were constructed with these waste materials. Load–settlement responses of the unreinforced and reinforced soils with a single stone column and a group of stone columns constructed with these waste materials were determined under the same loading conditions. The obtained results showed a very good improvement in the settlement behaviour of the loose sand. As a conclusion, local waste building materials can be used effectively for stone column construction. The use of these waste materials will contribute to recycling and environmental sustainability.

Experimental and Statistical Study on Single and Groups of Stone Columns

In the present study, 24 laboratory models on soft clay treated with stone columns were carried out. The results for each case are analysed for the purpose of constructing a statistical model linking the variables studied. The experiments showed that the stress concentration and bearing capacity of soil treated with stone column increase with increasing the undrained shear strength (cu), number of columns and L/d ratio. The models represent a single stone column and a group of stone columns. The studied variables are three dependent variables, the stress concentration ratio (n), bearing capacity of soil treated with stone column (q) and the settlement improvement ratio (Sr) due to the existence of stone columns. The independent variables are six: the undrained shear strength of clay soil, with three values (6, 9 and 12 kPa), the number of stone columns (1, 2, 3 and 4 columns) and the length (L) to the diameter (D) of the stone column or (L/D) ratio in two values (6 and 8). Besides, the bearing capacity of the soil treated (q) with stone columns and the settlement improvement ratio were used in some statistical models as independents. After regression analysis, a set of equations that correlate the previous variables have been suggested. The incepted values for dependent variables are close to the laboratory results.

Failure Process of a Single Stone Column in Soft Soil beneath Rigid Loading: Numerical Study

Abstract The discrete element method–finite difference method (DEM--FDM) numerical simulation was conducted to investigate the failure process and the bearing mechanism of the single stone column i...

Experimental and numerical study on the bearing capacity of encased stone columns

Stone columns have attracted considerable attention as a ground improvement techniques recently. Performance of stone columns, however, depends on confining pressure offered by the surrounding soils. In the case of very soft soils, the lateral confining pressure may be insufficient and this may lead to column bulging failure. Encapsulating the individual stone column enhances the lateral resistance against bulging by additional confining pressure. In this study, the influences of the length of encasement and type of aggregate materials on the bearing capacity of a single stone column in both dry sand and clay bed were investigated. The results indicated a clear improvement by encasing the half-length of the column. The numerical study also showed the effect of reinforcement stiffness reduces with increase in the cohesion of the clay. Parametric study showed that the effect of encasement stiffness is insignificant for clay bed with high values of cohesion.

Effect of Stress Concentration Ratio on Shear Strength of Soft Soils Improved with Stone Columns

Numerous studies have been performed on the behavior of stone columns subjected to vertical loads. However, little research has been focused on determining the shear strength and equivalent shear strength parameters of cohesive soils reinforced with stone columns. The performed research in this area mostly includes numerical analyses which do not consider the effect of stress concentration ratio, and the value of stress concentration ratio in such analyses is assumed to be 1. In this study, an experimental investigation has been carried out on stone columns subjected to vertical and shear loads, with the purpose of determining the actual value of stress concentration ratio. The experiments were performed in a large direct shear device. In this study, single, square and triangular arrangements of stone columns with three different area replacement ratios under three vertical loads were investigated. Soft clay was used as bed material, and stone column material was either crushed stone or fine-grained sand. Results showed that stress concentration ratio decreased with the increase in stone column diameter and vertical stress and the value of stress concentration ratio is highest for square arrangement and lowest for single stone columns. The equivalent shear parameters obtained from experiments and those predicted by analytical relationships were compared at stress concentration value of 1 and stress concentration values obtained from the experiments. Results also showed that the shear strength value and the equivalent shear strength parameters measured from experiments were higher than those predicted by analytical relationships.

Use of recycled materials in floating stone columns

In this research, to improve the bearing capacity of a soft clay bed, the performance of floating stone columns constructed of recycled aggregates from demolition waste was investigated. For this purpose, a single stone column with three types of materials, including recycled crushed brick (CB), recycled crushed concrete (CC) and gravel as natural aggregates was modelled. Furthermore, the quality of the recycled aggregates used was evaluated by aggregate index tests such as the aggregate crushing value and the aggregate impact value. The results of the recycled aggregate index tests demonstrated a poorer performance of these materials compared to the natural aggregate. Despite this, the bearing capacity of the clay bed reinforced with the floating column, which was filled with CB or CC, was approximately five times the bearing capacity of the unreinforced clay bed. Moreover, the loading results showed that the floating stone columns constructed of a type of aggregate delivered a better performance in comparison with the columns constructed of a combination of several types of recycled aggregates together or a combination of natural and recycled aggregates.

Performance of encased single stone column in layered soil

Stone columns were found to be effective, economical and widely-used ground improvement technique in soft grounds. It is important to understand the behavior of stone columns when they are installed in layered soils. This paper presents results from a series of small scale laboratory model tests carried out in unit cell tank to investigate the behavior of floating and end bearing stone columns in layered soils with and without encasement, consisting of loose sand overlying a soft soil. Tests were conducted with loading only the stone column area to estimate the limiting axial capacity of stone column. Laboratory tests were carried out on a column of 10 cm diameter surrounded by layered soil. Test results indicated that the bearing capacity of layered soil has been improved in all cases of stone column applications. The non- encased floating stone columns gave better results than non-encased end bearing stone column. The inclusion of geotextile encasement resulted in further improvement of layered soil and the encased floating stone column had superior bearing capacity improvement.

Behavior of Geotextile-Encased Single Stone Column in Soft Soils

Stone columns have become a widely used method of increasing bearing capacity of soft soils. This study investigates floating stone columns with and without encasement in soft soils. Although the stone columns in single-layered soil have been studied extensively, stone columns constructed in a base of varying soil layers are not fully understood. In the present study, the behavior of both single-layered soft soil and layered soil consisting of loose sand overlaying the soft soil was investigated by using small-scale laboratory pilot tests. The bearing capacity of soft soil was improved in all cases of stone column application. The contribution of stone columns on the bearing capacity of soft soil was presented by the term bearing improvement ratio (BIR). With a non-encased stone column in single-layered soft soil, the BIR was about 3.3-fold and with geotextile encasement in the same soil, the improvement ratio increased to 3.4-fold. For a non-encased stone column in layered soils, the BIR was about 2.0-fold and with geotextile enhancement in the same soil, this improvement ratio increased to 4.0-fold. The inclusion of geotextiles resulted in improved bearing capacity by distributing the induced stresses over larger areas. The maximum bulging of non-encased stone column in single-layered soft soil was observed at the depth of 1.5 times the original diameter of the stone column from the top, whereas for encased stone column in single-layered soft soil, the maximum bulging was transferred to a depth of 3.0 times the original diameter of the stone column.

Laboratory Study on Single Stone Columns Reinforced with Steel Bars and Discs

Stone columns are widely used as an effective and environmental friendly improvement method for increasing the load-carrying capacity of soft clay soils. In very soft clay soils, reinforced stone columns are used because of the lack of the lateral confinement created by the surrounding soil. To provide lateral additional confinement, geosynthetics are usually used. This study intends to evaluate the use of vertical steel bars and horizontal steel discs as an alternative way to geosynthetics to investigate the effect of reinforcement on the footing load-carrying characteristics. Therefore, some large-scale laboratory tests were conducted on stone columns with diameters of 80 and 100 mm and a length to diameter of 5. The results show that changing the arrangement of the bars to a higher stiffness leads to increase in load-carrying capacity. Reinforcing the full-length of the stone columns with the bars in comparison to half-length reinforced has significant influence in capacity. However, in the case of horizontal discs, this increase is negligible. Also by decreasing the space of the discs, load-carrying capacity increases. Moreover, the performance of the vertical reinforced stone column seemed to be better than the horizontal reinforced stone column. The increase of load-carrying capacity in reinforced stone columns with vertical bars or horizontal discs is higher than geotextile reinforcement in the same conditions.

The Experimental Design of Stone Columns' Modelling using Small-Scale Unit Cells: A Review

This paper presents a review of the experimental design of the small-scale single stone column that adopts the unit cell concept. Materials and methods used in experiments along with their effects and implication have been appraised. The reviewed cases showed that clayey soils were often used to construct the host ground. Steel cylindrical tanks were used with diameters ranging from 15 to 60 cm and heights ranging from 20 to 120 cm. For such scale, the used stone size is 2 to 10 mm. Plates load test can be carried out on the entire tank or on the stone column. The load has been imposed at a constant settlement rate of 1 to 1.25 mm/min in order to simulate the stage immediately after construction. The review shows that remoulding and replacement have been often practised for the construction of the host ground and the stone column, respectively.