This paper studies the advantages of geocell reinforcement on the performance of earth embankments constructed over weak foundation soil through laboratory model tests and proposes a simple method for the design of geocell-supported embankments. Model embankments were constructed above a layer of geocells formed using geogrids on top of a soft clay bed prepared in a steel test tank. Uniform surcharge pressure was applied on the crest and pressure-deformation behavior of the embankment and strains in the walls of geocells were monitored continuously until the failure was reached. The influence on the behavior of the embankment of various parameters - like tensile stiffness of geocell material, height and length of geocell layer, pocket-size of the cell, pattern of formation of geocells, and type of fill material inside the cells - was studied. Geocell reinforcement was found to be advantageous in increasing the load-bearing capacity and reducing the deformations of the embankments. The experimental results were validated using a general purpose slope-stability program and a design procedure useful for the preliminary design of geocell-supported embankments is illustrated. © 2006 ASCE.

K Rajagopal

Department Of Civil Engineering

N. R. Krishnaswamy

Deformation

Foundations

Geosynthetic materials

Mathematical models

Reinforcement

Slope stability

Stiffness

Strain

geocell reinforcement

Geogrids

Model tests

Embankments

EMBANKMENT

Geosynthetics

reinforced earth

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

Experimental and Theoretical Investigations on Geocell-Supported Embankments

International Journal of Geomechanics

This paper presents the finite-element simulations of the behavior of strip footings resting on sand beds, with different density of soil, reinforced with geocells of different dimensions. The strength and stiffness of sand confined with geocells is represented by an equivalent composite model developed from triaxial compression tests. The additional confining pressure due to geocells, calculated using hoop tension theory, is used to obtain the apparent cohesive strength imparted to sand due to geocells. The elastic modulus of the geocell encased sand is related to the elastic modulus of the unreinforced sand and the tensile modulus of the geocell material using an empirical equation. Load-settlement response of strip footings on geocell reinforced sand beds obtained from the numerical simulations are compared with the corresponding experimental results and the match is found to be good. In addition, numerical results showed that with the provision of a geocell layer, the mobilized shear stress contours become horizontal and shift downwards, indicating that the geocell mattress transmits the footing load to a deeper depth, thereby bringing about a higher load carrying capacity. © 2009 ASCE.

Numerical simulation of the behavior of geocell reinforced sand in foundations

Experimental and theoretical investigations on geocell-supported embankments

Stone columns (or granular piles) are increasingly being used for ground improvement, particularly for flexible structures such as road embankments, oil storage tanks, etc. When the stone columns are installed in extremely soft soils, the lateral confinement offered by the surrounding soil may not be adequate to form the stone column. Consequently, the stone columns installed in such soils will not be able to develop the required load-bearing capacity. In such soils, the required lateral confinement can be induced by encasing the stone columns with a suitable geosynthetic. The encasement, besides increasing the strength and stiffness of the stone column, prevents the lateral squeezing of stones when the column is installed even in extremely soft soils, thus enabling quicker and more economical installation. This paper investigates the qualitative and quantitative improvement in load capacity of the stone column by encasement through a comprehensive parametric study using the finite element analysis. It is found from the analyses that the encased stone columns have much higher load carrying capacities and undergo lesser compressions and lesser lateral bulging as compared to conventional stone columns. The results have shown that the lateral confining stresses developed in the stone columns are higher with encasement. The encasement at the top portion of the stone column up to twice the diameter of the column is found to be adequate in improving its load carrying capacity. As the stiffness of the encasement increases, the lateral stresses transferred to the surrounding soil are found to decrease. This phenomenon makes the load capacity of encased columns less dependent on the strength of the surrounding soil as compared to the ordinary stone columns. © 2006 Elsevier Ltd. All rights reserved.

Geotextiles and Geomembranes

Geosynthetic-encased stone columns: Numerical evaluation

Fly ash produced from thermal power plants as byproduct requires large area for storage. The quantity of fly ash and its hazardous impact on the environment is continuously growing. Tireless efforts are being carried out by many researchers to utilize the fly ash in geotechnical applications. In the present study, the behavior of cellular reinforcement (geocell) in fly ash under the static triaxial tests is emphasized. Triaxial tests were conducted on unreinforced and reinforced fly ash sample of 75 mm diameter and 150 mm height. The cellular reinforcement is made up of used and wasted locally available plastic water bottles. The diameters of the reinforcement used in this present study are 35 and 50 mm, with thickness 1 mm. Four different heights of the reinforcement, 10, 20, 30 and 40 mm, are used for both the diameters to study the effect of cellular reinforcement. The tests were conducted by placing cellular reinforcement in one layer as well as in two layers. Deviator stress-strain patterns due to the effect of cellular reinforcement are studied under three different cell pressures 100, 150 and 200 kPa. Peak deviator stress and shear strength parameters are found increasing with increasing in the height of cellular reinforcement for both the diameters of reinforcement. The 50 mm diameter cellular reinforcement showed high peak deviator stress-strain and shear strength parameters over 35 mm diameter. The placement, number of layers, height and diameter of reinforcement are found to have effect on the peak deviator stress. Finite element simulation is carried out using Plaxis 2D professional version to envisage the failure patterns, horizontal displacement and deviator stress-strain patterns, and results of finite element simulation are found to be in reasonably good agreement with the experimental results. © 2013 W. S. Maney & Son Ltd

International Journal of Geotechnical Engineering

Study of cellular reinforced fly ash under triaxial loading conditions

Cellular reinforcement is a three dimensional reinforcement used for reinforced soil structures. Behaviour of such reinforcement is important for its use in actual practice. Present paper focuses on the behavior of cellular reinforcement in sand under the triaxial loading conditions. Series of triaxial tests are performed on unreinforced and reinforced sand with single layer as well as double layers of cellular reinforcements with 75 mm sample diameter. Six different reinforcement heights of cellular reinforcements (varying from 3 to 50 mm) are used along with one sheet reinforcement of thickness 1 mm. From the experimental failure patterns of the triaxial samples, multiple zones of failure are observed as an effect of cellular reinforcement. Deviator stress - strain curves are studied for single and double layers of cellular reinforcement under three different confining pressures. Peak deviator stress is found increasing with increasing height of cellular reinforcement, which shows the confining effect of cellular reinforcement. Shear strength parameters are evaluated and are found increasing with increase in height of cellular reinforcement, also cellular reinforcement with heights 10 mm and more have showed increased shear strength parameters, as compared to 1 mm thick sheet reinforcement. This assures better behavior performance of cellular reinforcement over the planar one. Failure patterns are also visualized by finite element analysis and found in accord with experimental observations Horizontal displacement for reinforced samples visualized multi-zoned failure pattern. Finite element results for deviator stress-strain relationship are found in reasonably good accord with experimental results. © Springer Science+Business Media B.V. 2009.

Geotechnical and Geological Engineering

Behaviour of cellular reinforced sand under triaxial loading conditions

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

Geotechnical Testing Journal

Model Studies on Geocell Supported Embankments Constructed Over a Soft Clay Foundation

Computers and Geotechnics

Analysis of geocell reinforced-soil covers over large span conduits

Performance of a road embankment on soft clay supported on a Geocell mattress foundation

Journal	International Journal of Geomechanics
ISSN	15323641
Open Access	No