Experimental and Theoretical Investigations on Geocell-Supported Embankments
01 Jan 2006-International Journal of Geomechanics (American Society of Civil Engineers)-Vol. 6, Iss: 1, pp 30-35
TL;DR: In this article, the advantages of geocell reinforcement on the performance of earth embankments constructed over weak foundation soil through laboratory model tests were studied. And the experimental results were validated using a general purpose slope-stability program.
Abstract: 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.
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TL;DR: In this article, the authors investigated the qualitative and quantitative improvement in load capacity of the stone column by encasement through a comprehensive parametric study using the finite element analysis and found 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.
Abstract: 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
264 citations
Cites background from "Experimental and Theoretical Invest..."
...(2) shown below (Bathurst and Karpurapu (1993); Rajagopal et al. (1999); Latha et al. (2006))....
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TL;DR: In this paper, a model and a simple bearing capacity calculation method for the geocell-supported embankment on the soft subgrade were proposed based on the study of the reinforcement functions of a geocell layer in a road embankments.
Abstract: Soil reinforcement using geocells has been utilized in many areas of geotechnical engineering. In this paper, a model and a simple bearing capacity calculation method for the geocell-supported embankment on the soft subgrade were proposed based on the study of the reinforcement functions of a geocell layer in a road embankment. The model and calculation procedures considered both the “vertical stress dispersion effect” and “membrane effect” of geocell reinforcement. They were verified by a laboratory experiment and compared with Koerner's method. The results indicated that the calculated results obtained from the present method were much closer to the experimental results than those from Koerner's method when the foundation settlement is large. The study also indicated that the installation of the geocell onto the crushed stone cushion significantly increased the bearing capacity of the soft subgrade.
156 citations
TL;DR: In this article, a beam model is used to simulate the geocell behavior as a flexible slab foundation which can carry both bending and membrane stresses for stability analysis of geocell reinforced slopes.
Abstract: Geocell reinforced soil may be used in many areas of geotechnical engineering, however, there is little information on analysis of the behavior of geocell reinforced slopes. Due to the height of the geocell, the geocell-reinforced mattress more likely provides a beam or plate effect than a planar membrane effect. The purpose of this paper is to use beam model to simulate the geocell behavior as a flexible slab foundation which can carry both bending and membrane stresses for stability analysis of geocell reinforced slopes. In addition, the interface resistance between the geocell–soil was considered. The Young's modulus of geocell encased soil was obtained from the elastic modulus of the unreinforced soil and the tensile modulus of the geocell reinforcement using an empirical equation. Parametric studies of geocell reinforced slope are carried out by varying placement depth of the geocell layer, number of geocell layers, vertical spacing between reinforcement layers, length, thickness and Young's modulus of the geocell reinforcement. The influence of slope geometry, shear strength properties and soil compaction on the behavior of geocell reinforced slope is also discussed. The obtained results show that geocell reinforcement acts as a wide slab and thus it can restrain the failure surface from developing and redistribute the loads over a wider area. Therefore, under the geocell placement, the lateral deformation and shear strain values of the slope considerably decrease. Furthermore, the effective placement of geocell reinforcements is found to be between the middle of the slope and the middle of critical failure surface of the unreinforced slope.
93 citations
Cites background from "Experimental and Theoretical Invest..."
...Recently, the beneficial effects of using geocell to increase load-carrying capacity of soil and decrease footing settlement has been investigated by several researchers (Dash et al., 2003, 2004; Krishnaswamy et al., 2000; Leshchinsky and Ling, 2013b; Latha et al., 2006; Latha and Murthy, 2007; Moghaddas Tafreshi and Dawson, 2010a, b; Moghaddas Tafreshi and Dawson, 2012; Sireesh et al., 2009; Tavakoli Mehrjardi et al., 2012; Yang et al., 2012; Zhang et al., 2010a,b; Zhou and Wen, 2008)....
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...In the literature, there is evidence to show that equivalent composite model is appropriate to simulate the geocell behavior (Latha et al., 2006; Latha and Rajagopal, 2007; Latha et al., 2008, 2009)....
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TL;DR: In this article, the authors presented the case history of the construction of a 3 m high embankment on the geocell foundation over the soft settled red mud, which is a waste product from the Bayer process of aluminum industry.
Abstract: This paper presents the case history of the construction of a 3 m high embankment on the geocell foundation over the soft settled red mud. Red mud is a waste product from the Bayer process of Aluminum industry. Geotechnical problems of the site, the design of the geocell foundation based on experimental investigation and the construction sequences of the geocell foundations in the field are discussed in the paper. Based on the experimental studies, an analytical model was also developed to estimate the load carrying capacity of the soft clay bed reinforced with geocell and combination of geocell and geogrid. The results of the experimental and analytical studies revealed that the use of combination of geocell and the geogrid is always beneficial than using the geocell alone. Hence, the combination of geocell and geogrid was recommended to stabilize the embankment base. The reported embankment is located in Lanjigharh (Orissa) in India. Construction of the embankment on the geocell foundation has already been completed. The constructed embankmenthas already sustained two monsoon rains without any cracks and seepage.
90 citations
Cites methods from "Experimental and Theoretical Invest..."
...Madhavi Latha (2000) proposed FEM based approach to design of the geocell reinforced embankment based on the equivalent composite approach....
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...Further, based on the equivalent composite approach, Madhavi Latha et al. (2006) proposed the slope stability based design approach to design the geocell supported embankment....
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...Many researchers have reported the beneficial effects of geocells (Dash et al., 2001a; Sitharam and Sireesh, 2005; Zhou and Wen, 2008; Madhavi Latha and Somwanshi, 2009; Sireesh et al., 2009; Moghaddas Tafreshi and Dawson, 2010; Pokharel et al., 2010; Lambert et al., 2011; Moghaddas Tafreshi and Dawson, 2012; Tavaloli Mehrjardi et al., 2012; Yang et al., 2012; Thakur et al., 2012; Mehdipour et al., 2013; Leshchinsky and Ling, 2013)....
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TL;DR: In this article, the results from parametric finite element analyses of geocell-supported embankments constructed on weak foundation soils are presented, and a composite model is used to numerically simulate the results.
Abstract: 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 ...
77 citations
Additional excerpts
...This mesh arrangement was reported to be accurate in predicting limit loads in plane strain problems (Nagtegaal et al. 1974). Rowe and Soderman (1987) have reported good success in using this type of mesh arrangement in simulating many reinforced soil embankment problems....
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References
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TL;DR: In this article, a large number of triaxial compression tests were performed on granular soil encased in single and multiple geocells to investigate the effect of the stiffness of the geocell on the overall performance of geocell-soil composite.
Abstract: 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.
212 citations
TL;DR: In this paper, the results of a series of large-scale triaxial tests carried out on 200mm-high isolated geocell-soil composite specimens and unreinforced soil specimens were described.
Abstract: The paper describes the results of a series of large-scale triaxial tests carried out on 200-mm-high isolated geocell-soil composite specimens and unreinforced soil specimens. Two different aggregate soils were used in the test program. The reinforced specimens were tested with a height-to-diameter ratio of unity, which matches the dimensions of these systems in a typical base reinforcement application. The results illustrate the stiffening effect and strength increase imparted to the soil by the enhanced confinement effect. Comparison of reinforced and unreinforced soil specimens shows that the frictional resistance described by the peak friction angle of the soil infill is applicable to the composite structure as well. A simple elastic membrane model can be used to estimate the additional apparent cohesion present in the composite structure.
196 citations
TL;DR: In the undrained triaxial compression test the rubber membranes enclosing the specimens give rise to an apparent increase in strength as mentioned in this paper, and the results of tests to determine the magnitide of this effect together with an approximate theoretical treatment.
Abstract: Synopsis In the undrained triaxial compression test the rubber membranes enclosing the specimens give rise to an apparent increase in strength. This article presents the results of tests to determine the magnitide of this effect together with an approximate theoretical treatment. Triaxial tests on remoulded London clay, employing rubber membranes of three different thicknesses, when compared with unconfined compression tests at the same moisture content show that the strength contributed by the rubber membrane is:— independent of specimen strength proportional to the stiffness of the membrane independent of cell pressure. In compression tests, with the specimen enclosed in a rubber membrane but with no lateral pressure, the effect is smaller than in the normal triaxial test. Filter paper drains, used to accelerate consolidation, add further to the compression strength and consequently a larger correction must be applied to the measured strength. A method for estimating the rubber correction from a simple ...
129 citations
TL;DR: In this paper, the results of laboratory model tests on geocell-supported earth embankments constructed over a soft clay foundation were described, and the vertical and horizontal deformations and the strains developed within the geocell layer were measured during the test.
Abstract: This paper describes the results of laboratory model tests on geocell-supported earth embankments constructed over a soft clay foundation. The soft clay foundation was prepared in a large test tank to a depth of 600 mm. A single geocell layer was formed on this clay foundation with different thicknesses, and embankments were constructed above this layer. Four different types of geogrids were used for the formation of the geocell layer. The embankments were subjected to uniform surcharge pressure on the crest until failure. The vertical and horizontal deformations and the strains developed within the geocell layer were measured during the test. The influence of various parameters such as tensile stiffness of geogrids used to fabricate the geocell material, height, and pocket-size of the geocell layer, length of the geocell layer, and type of fill material inside the geocell on the behavior of the embankments was investigated through a series of laboratory tests.
115 citations
TL;DR: In this paper, the authors describe the unique features of a geocell foundation mattress formed from polymer grid reinforcement and show how increased bearing capacity can be developed in a soft foundation using slip line fields and taking advantage of these unique features.
Abstract: This paper describes the unique features of a geocell foundation mattress formed from polymer grid reinforcement. It shows how increased bearing capacity can be developed in a soft foundation using slip line fields and taking advantage of these unique features. Operations to construct the geocell foundation mattress are described and practical advantages to the contractor are identified. Case histories of monitored performance show how effective the geocell foundation mattress is in reducing overall embankment settlement and also in reducing differential settelement over variable soft ground. Finally, costs of construction are examined, and the geocell solution shows cost advantages over traditional methods of construction on soft foundations.
104 citations