This paper presents an equivalent continuum method for simulating the behaviour of geocell reinforced sand foundation beds, using finite element technique. An equivalent composite model is used for numerically simulating the improvement in the strength and stiffness of sand confined with geocells. Shear strength of geocell encased sand is derived from the additional confining pressure due to geocell using hoop tension theory. The stiffness of geocell encased sand is represented by an empirical equation in terms of the stiffness of the unreinforced sand and the tensile modulus of the geocell material. Numerical simulations of strip footings resting on sand bed are carried out with and without geocell layer, varying parameters like, the dimensions of geocell layer, pocket size, depth of placement of geocell layer and the tensile modulus of the geocell material. The results of numerical analyses are validated with the corresponding experimental results. The comparison between the numerical results and the experimental results is found to be reasonably good. Some significant observations on the mechanism of geocell reinforcement have been presented in this paper. © Springer Science+Business Media B.V. 2008.

K Rajagopal

Department Of Civil Engineering

Computer simulation

Elastic moduli

Equivalence classes

finite element method

Reinforcement

sand

Shear strength

Stiffness

Thermoelectricity

(2+1) DIMENSIONS

(e ,2e) theory

BUSINESS MEDIA

COMPOSITE MODELING

Confining pressures

Empirical equations

EQUIVALENT CONTINUUM

Experimental results

FINITE ELEMENT TECHNIQUES

Geocell

geocell reinforcement

Geocells

Numerica l results

Numerical simulations

reinforced sand

SAND BEDS

Springer (CO)

Strength (IGC: D5/D6)

strip footings

TENSILE MODULUS

Varying parameters

Numerical analysis

Footing

geotextile

Model test

numerical model

soil reinforcement

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Geotechnical and Geological Engineering

Many of the pavement structures fail well before their design life owing to the poor quality of construction materials, inadequate compaction, inadequate preparation of the subgrade, overloading, etc. Two options are available to improve the longevity of the pavement. The first option is by increasing the thickness of different pavement layers and the other option is by increasing the rigidity of the layers within the system so as to reduce the stresses transferred to the lower layers. Of these two methods it has been widely observed that increasing the strength and rigidity of the pavement layers is a more efficient method to lower the stresses on the pavement layers thereby increasing the life of the pavement. In the present research work, the improvement in the strength and stiffness of the subbase layer in a flexible pavement system through the use of geosynthetic layers was investigated by conducting field plate load tests and a series of laboratory plate load tests. The improvement in the strength of the pavement is reflected by the increase in modulus of the section reinforced with geosynthetic layers. This paper will describe the field and laboratory tests, interpretation of the data from these tests, and the application of this data for design of flexible pavements and their economic analyses. © 2014 W. S. Maney & Son Ltd.

International Journal of Geotechnical Engineering

Studies on geosynthetic-reinforced road pavement structures

This paper presents the results from parametric finite element analyses of geocell-supported embankments constructed on weak foundation soils. A composite model is used to numerically simulate the improvement in the strength and stiffness of the soil as a result of geocell confinement. The shear strength of the geocell-encased soil is obtained as a function of the additional confining pressure due to the geocell encasement considering it as a thin cylinder subjected to internal pressure. The stiffness of the geocell-encased soil is obtained from the stiffness of the unreinforced soil and the tensile modulus of the geocell material using an empirical equation. The validity of the model is verified by simulating the laboratory experiments on model geocell-supported embankments. Parametric finite element analyses of the geocell-supported embankments are carried out by varying the dimensions of the geocell layer, the tensile strength of the material used for fabricating the geocell layer, the properties of the infill soil, and the depth of the foundation layer. Some important guidelines for selecting the geocell reinforcement to support embankments on weak foundation soils are established through these numerical studies. © 2007 NRC Canada.

Canadian Geotechnical Journal

Parametric finite element analyses of geocell-supported embankments

This paper presents the results from laboratory-model tests on a strip footing supported by a sand bed reinforced with a geocell mattress. The parameters varied in the testing program include pattern of geocell formation, pocket size, height and width of geocell mattress, the depth to the top of geocell mattress, tensile stiffness of the geogrids used to fabricate geocell mattress and the relative density of the sand. With the provision of geocell reinforcement, failure was not observed even at a settlement equal to 50% of the footing width and a load as high as 8 times the ultimate bearing capacity of the unreinforced sand. Based on the model test results, the depth of placement and the dimensions of the geocell layer for mobilising maximum bearing capacity improvement have been determined. In addition to the tensile strength of reinforcement, the aperture size and orientation of ribs of the geogrid used to fabricate geocell mattress must be taken into account while evaluating its contribution to the improvement in the performance. © 2001 Elsevier Science Ltd. All rights reserved.

Geotextiles and Geomembranes

Bearing capacity of strip footings supported on geocell-reinforced sand

This paper studies the influence of geocell confinement on the strength and stiffness behaviour of granular soils. A large number of triaxial compression tests were performed on granular soil encased in single and multiple geocells. The geocells were fabricated by hand using different woven and nonwoven geotextiles and soft mesh to investigate the effect of the stiffness of the geocell on the overall performance of geocell-soil composite. In general, it was observed that the granular soil develops a large amount of apparent cohesive strength due to the confinement by the geocell. The magnitude of this cohesive strength was observed to be dependent on the properties of the geosynthetic used to fabricate the geocell. The stiffness of the composite was also found to increase with the provision of geocell reinforcement. The results have shown that using three interconnected cells in the testing programme is adequate to simulate the performance of geocell reinforcement layer consisting of many interconnected cells. A simple methodology has been presented in the paper to estimate the magnitude of the apparent cohesive strength developed by the granular soil as a function of the geometric and material properties of the geocell.This paper studies the influence of geocell confinement on the strength and stiffness behaviour of granular soils. A large number of triaxial compression tests were performed on granular soil encased in single and multiple geocells. The geocells were fabricated by hand using different woven and nonwoven geotextiles and soft mesh to investigate the effect of the stiffness of the geocell on the overall performance of geocell-soil composite. In general, it was observed that the granular soil develops a large amount of apparent cohesive strength due to the confinement by the geocell. The magnitude of this cohesive strength was observed to be dependent on the properties of the geosynthetic used to fabricate the geocell. The stiffness of the composite was also found to increase with the provision of geocell reinforcement. The results have shown that using three interconnected cells in the testing programme is adequate to simulate the performance of geocell reinforcement layer consisting of many interconnected cells. A simple methodology has been presented in the paper to estimate the magnitude of the apparent cohesive strength developed by the granular soil as a function of the geometric and material properties of the geocell.

Behaviour of sand confined with single and multiple geocells

The Paper describes finite element models that are used to simulate the behaviour of two carefully constructed and monitored large-scale geosynthetic reinforced soil retaining walls. The walls were constructed using a dense sand fill and layers of extensible polymeric (geosynthetic) reinforcement attached to two very different facing treatments. The model walls were taken to collapse using a series of uniform surcharge loads applied at the sand fill surface. The Paper demonstrates that correct modelling of the dilatant behaviour of the sand soil is required to give accurate predictions of wall performance. A modified form of hyperbolic constitutive model that includes a dilation parameter is adopted to model the behaviour of the granular soil. Mechanical properties of the constituent components of the large-scale physical models are established using standard laboratory tests including constant load tests on the polymeric reinforcement from which isochronous load-strain-time data is developed. The results of analyses show that the finite element model, constitutive models and implementation reported in this study can accurately predict all important features of wall performance. © 1995.

Computers and Geotechnics

Behaviour of geosynthetic reinforced soil retaining walls using the finite element method

Model studies of a circular footing supported on geocell-reinforced clay

Equivalent continuum simulations of geocell reinforced sand beds supporting strip footings

Journal	Geotechnical and Geological Engineering
ISSN	09603182
Open Access	No