The undrained cohesion of the soil as a criterion for column installation with a depth vibrator

Wehr, Jimmy

doi:10.1201/b13890-35

Cited by 6 publications

(6 citation statements)

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“…The effectiveness of its performance is mainly based on the soil-column load distribution, which largely depends on the lateral support provided by the soft soil. In very soft soils, with undrained shear strengths lower than some limit between 15 and 5 kPa (Wehr, 2006), this lateral support is not sufficient, and columns may fail because of excessive bulging (McKenna et al, 1975). In these situations, one widely employed solution to enhance the performance of this treatment is to wrap the columns with a geosynthetic encasement.…”

Section: Introductionmentioning

confidence: 99%

Influence of geotextile encasement on the behaviour of stone columns: Laboratory study

Miranda

Costa

Castro

et al. 2017

Geotextiles and Geomembranes

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Section: Introductionmentioning

confidence: 99%

Influence of geotextile encasement on the behaviour of stone columns: Laboratory study

Miranda

Costa

Castro

et al. 2017

Geotextiles and Geomembranes

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“…Very soft soils may not provide enough lateral support for a proper performance of a stone column treatment. The undrained shear strength of the surrounding soil is generally used as the criterion to decide the feasibility of the treatment, with lower bound in the range 5e15 kPa (Wehr, 2006). In recent years, geotextile encasement has been successfully used to extend the use of stone columns to extremely soft soils.…”

Section: Introductionmentioning

confidence: 99%

Deformation and consolidation around encased stone columns

Castro

Sagaseta

2011

Geotextiles and Geomembranes

113

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a b s t r a c tA new analytical solution is presented to study soft soil improvement by means of encased stone columns to reduce both settlement and consolidation time. The proposed solution aims to be a simple and useful tool for design. Only a unit cell, i.e. an end-bearing column and its surrounding soil, is modelled in axial symmetry under a rigid and uniform load. The soft soil is treated as an elastic material and the column as an elasticeplastic material using the MohreCoulomb yield criterion and a nonassociated flow rule, with a constant dilatancy angle. An elasto-plastic behaviour is also considered for the encasement by means of a limit tensile strength. The solution is presented in a closed form and is directly usable in a spreadsheet. Parametric studies of the settlement reduction, stress concentration and consolidation time show the efficiency of column encasement, which is mainly ruled by the encasement stiffness compared to that of the soil. Column encasement is equally useful for common area replacement ratios but columns of smaller diameters are better confined. Furthermore, the applied load should be limited to prevent the encasement from reaching its tensile strength limit. A simplified formulation of the solution is developed assuming drained condition. The results are in agreement with numerical analyses.

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“…The undrained shear strength (

) of natural soft soil is generally used as the limiting parameter for stone column feasibility. A limiting value around 5–15 kPa [ 4 ] may be adopted. To improve the lateral confinement of stone columns in those extremely soft soils, encasing the columns with geotextiles or other geosynthetics, such as geogrids, has proven to be a successful technique in recent times (e.g., [ 5 ]).…”

Section: Introductionmentioning

confidence: 99%

Modeling Stone Columns

Castro

2017

Materials

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This paper reviews the main modeling techniques for stone columns, both ordinary stone columns and geosynthetic-encased stone columns. The paper tries to encompass the more recent advances and recommendations in the topic. Regarding the geometrical model, the main options are the “unit cell”, longitudinal gravel trenches in plane strain conditions, cylindrical rings of gravel in axial symmetry conditions, equivalent homogeneous soil with improved properties and three-dimensional models, either a full three-dimensional model or just a three-dimensional row or slice of columns. Some guidelines for obtaining these simplified geometrical models are provided and the particular case of groups of columns under footings is also analyzed. For the latter case, there is a column critical length that is around twice the footing width for non-encased columns in a homogeneous soft soil. In the literature, the column critical length is sometimes given as a function of the column length, which leads to some disparities in its value. Here it is shown that the column critical length mainly depends on the footing dimensions. Some other features related with column modeling are also briefly presented, such as the influence of column installation. Finally, some guidance and recommendations are provided on parameter selection for the study of stone columns.

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The undrained cohesion of the soil as a criterion for column installation with a depth vibrator

Cited by 6 publications

References 0 publications

Influence of geotextile encasement on the behaviour of stone columns: Laboratory study

Influence of geotextile encasement on the behaviour of stone columns: Laboratory study

Deformation and consolidation around encased stone columns

Modeling Stone Columns

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