Column Supported Embankments with Geosynthetic Encased Columns: Validity of the Unit Cell Concept

Khabbazian, Majid; Kaliakin, Victor N.; Meehan, Christopher L.

doi:10.1007/s10706-014-9826-8

Cited by 41 publications

(12 citation statements)

References 37 publications

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“…The support provided by the soil surrounding the column increases as the depth increases, but at the top of the column bulging failure is the most general mechanism for column failure. Khabbazian et al(2015) [12] also suggested the same results. Zhng and Zhao (2012) [17] verified the method of installation of stone column by comparing it with two different solutions.…”

Section: Literature Surveysupporting

confidence: 64%

Effect of Grouted Granular Column on the Load Carrying Capacity of the Expansive soil

Verma*¹,

Sahu²

2019

IJRTE

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Due to the scarcity of land for the construction of industrial, commercial, and transportation structures for development in urban areas, it is very necessary to use the places which have weak strata. This has become very mandatory to use the land which has poor engineering properties due to the unavailability of land. In the recent years granular columns have come under the extensive use for increasing the load carrying capacity and reducing the settlement in the expansive soil and loose sand. Nowadays to increase the stability of the foundation, granular columns are being widely used. Traditional columns are driven into the weak expansive soil stratum and maintain its stability from lateral confinement, which is generally due to the reaction from the surrounding stiffened expansive soil. However, this is not so easy to support loose soil, an additional lateral support may have to be provided to stabilize it and reduce its settlements. This study aims to overcome this weakness in soil by wrapping the granular column in geotextile layer to enhance the lateral reinforcement. In the present paper the discussion is about the variation in load carrying capacity and settlement characteristics of granular column (made up of cement fly ash and sand in a definite proportion instead of aggregates and stones) and analyzing its effect on the expansive soil by comparing its results with geotextile encased columns. In this process the study investigates the improvement of load carrying capacity of a single granular column encased with geotextile through model test.

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Section: Literature Surveysupporting

confidence: 64%

Effect of Grouted Granular Column on the Load Carrying Capacity of the Expansive soil

Verma*¹,

Sahu²

2019

IJRTE

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“…Nowadays, 3D numerical codes are fairly easy to access and to use; so, there are some authors that study the unit cell as a full 3D problem, i.e., considering the hexagonal or square prism. Nevertheless, the differences between the full 3D prism and the two-dimensional (2D) model (cylinder) in axial symmetry are negligible [ 30 , 31 ]. The simplicity of the unit cell model has recently led to highly advanced numerical models, such as that presented by Indraratna et al [ 32 ], where the column is modelled using 2D discrete elements to represent the gravel particles.…”

Section: Unit Cellmentioning

confidence: 99%

“…Finally, the unit cell is an appropriate simplified geometrical model to study the settlement and its evolution with time at the center of an embankment, but obviously it is not valid for studying the stability of the lateral slopes ( Table 1 ). For similar reasons, it does not allow the lateral spreading and the contribution of a geosynthetic reinforcement that acts as a “blanket” or “bridging layer” over the columns and soft soil foundation (geosynthetic reinforced and column supported embankments, GRCSE) to be studied [ 31 ]. To study the lateral spreading of the embankment, the unit cell model may be improved by substituting the horizontally-fixed external lateral boundary by elastic springs [ 39 ].…”

Section: Unit Cellmentioning

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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“…Several other studies have been conducted using two dimensional numerical models of geosynthetic reinforced column supported embankment structures adopting the finite element method (FEM) and finite difference method (FDM) (Han et al, 2007;Huang and Han, 2010;Yapage and Liyanapathirana, 2014). Furthermore, the predictions adopting full-width model were compared with unit cell model in numerical simulations by Bhasi and Rajagopal (2015), Khabbazian et al (2015), and Yu and Bathurst (2017). Collin et al (2005) proposed a mechanical model of multiple layers of low strength geogrids within the LTP based on the concept of "beam" theory.…”

Section: Introductionmentioning

confidence: 99%

Analytical study for double-layer geosynthetic reinforced load transfer platform on column improved soft soil

Ghosh

Fatahi

Khabbaz

et al. 2017

Geotextiles and Geomembranes

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The objective of this study is to propose a reasonably accurate mechanical model for double-layer geosynthetic reinforced load transfer platform (LTP) on column reinforced soft soil which can be used by practicing engineers. The developed model is very useful to study the behaviour of LTP resting on soft soil improved with conventional columns such as concrete columns, piles, and deep soil mixing columns. The negligible tensile strength of granular material in LTP, bending and shear deformations of LTP, compressibility and shearing of soft soil have been incorporated in the model. Furthermore, the results from the proposed model simulating the soft soil as Kerr foundation model are compared to the corresponding solutions when the soft soil is idealised by Winkler and Pasternak foundation models. It is observed from the comparison that the presented model can be used as a tool for a better prediction of the LTP behaviour with multi layers of geosynthetics, in comparison with the situation that soft soil is modelled by Winkler and Pasternak foundations. Furthermore, parametric studies show that as the column spacing increases, the maximum deflection of LTP and normalised tension in the geosynthetics also increase. Whereas, the maximum deflection of LTP and normalised tension in the geosynthetics decrease with increasing LTP thickness, stiffness of subsoil, and stiffness of geosynthetic reinforcement. In addition, it is observed that the use of one stronger geosynthetic layer (e.g. 1×2000 kN/m) with the equivalent stiffness of two geosynthetic layers (e.g. 2×1000 kN/m) does not result in the same settlement of LTP and the tension of the geosynthetic reinforcement when compared to two weaker geosynthetic layers.

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Column Supported Embankments with Geosynthetic Encased Columns: Validity of the Unit Cell Concept

Cited by 41 publications

References 37 publications

Effect of Grouted Granular Column on the Load Carrying Capacity of the Expansive soil

Effect of Grouted Granular Column on the Load Carrying Capacity of the Expansive soil

Modeling Stone Columns

Analytical study for double-layer geosynthetic reinforced load transfer platform on column improved soft soil

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