Numerical Simulation of the Behavior of Geocell Reinforced Sand in Foundations
01 Aug 2009-International Journal of Geomechanics (American Society of Civil Engineers)-Vol. 9, Iss: 4, pp 143-152
TL;DR: In this paper, a finite-element simulation of the behavior of strip footings resting on sand beds, with different density of soil, reinforced with geocells of different dimensions, is presented.
Abstract: 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 b...
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TL;DR: In this article, the results of laboratory-model tests on strip footings supported on unreinforced and geocell-reinforced sand beds under a combination of static and repeated loads are presented The influences of various parameters are studied including reinforcement width, height of the geocell below the footing base and various amplitudes of repeated load.
Abstract: The results of laboratory-model tests on strip footings supported on unreinforced and geocell-reinforced sand beds under a combination of static and repeated loads are presented The influences of various parameters are studied including reinforcement width, height of the geocell below the footing base and various amplitudes of repeated load Mostly, a stable, resilient response is observed once incrementally accumulated plastic strain has ceased (usually during the first 10 cycles of loading) The reinforcement reduces the magnitude of the final settlement, acts as a settlement retardant, permits higher loads or increased cycling The reinforcement’s efficiency in reducing the maximum footing settlement decreased as the height and width of geocell were increased Plastic deformation was limited by geocells more under repeated loading than under a similar static loading, with the reduction being greatest when more reinforcement was present and when the loading rate was fastest It is deduced that the greater resilient stiffness of a rapidly loaded polymeric geocell attracts load to itself thereby protecting the soil from some of the more challenging stress states and, hence, reduces deformation Simple dimensional analysis showed the need for an increased stiffness of the geosynthetic components in order to deliver full-scale performance similitude
105 citations
Cites background from "Numerical Simulation of the Behavio..."
...…Rajagopal, 2007; Chen and Chiu, 2008; Yoon et al., 2008; Zhou and Wen, 2008; Sireesh et al., 2009; Wesseloo et al., 2009; Ling et al., 2009; Madhavi Latha et al., 2009; Zhang et al., 2010; Pokharel et al., 2010; Leshchinsky et al., 2010; Lambert et al., 2011; Moghaddas Tafreshi et al., 2011; Yang…...
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...In recent decades, due to its economy, ease of construction and performance, reinforced soil has been widely exploited in geotechnical engineering applications such as in the construction of roads, railway embankments, retaining wall, stabilization of slopes and improvement of soft ground (Shin and Das, 2000; Bathurst et al., 2003, 2009; Blatz and Bathurst, 2003; Deb et al., 2005; Sitharam et al., 2005, 2007; Dash et al., 2007; Guler et al., 2007; Laman and Yildiz, 2007; Madhavi Latha and Rajagopal, 2007; Chen and Chiu, 2008; Yoon et al., 2008; Zhou and Wen, 2008; Sireesh et al., 2009; Wesseloo et al., 2009; Ling et al., 2009; Madhavi Latha et al., 2009; Zhang et al., 2010; Pokharel et al., 2010; Leshchinsky et al., 2010; Lambert et al., 2011; Moghaddas Tafreshi et al., 2011; Yang et al., 2011)....
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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
TL;DR: In this article, a review of the developments and state-of-the-art pertinent to geocell research and field practices is presented, with a discussion on the research gaps in the subject area.
Abstract: In the last few years, the use of geocell reinforcements in various infrastructural projects has gained importance due to its positive benefits. This paper reviews the developments and state-of-the-art pertinent to geocell research and field practices. The geocell studies covering, experimental, numerical, analytical and field performances have been reviewed. Characterization of the geocell has been discussed in detail. The field investigations of the test sections and the performance of the in-service geocell supported structures have been reviewed. A note has been presented on current research trends and the future prospects. A summary of the past research findings has been presented with a discussion on the research gaps in the subject area. It is evident from the past studies that the geocell is evolving as a promising sustainable ground reinforcement technique. Due to an increased use of geocells in the infrastructure projects, there exists an expansive scope for further research to understand the material better.
72 citations
Cites methods from "Numerical Simulation of the Behavio..."
...[65] ECA with Duncan-Chang model 2-D/GEOFEM Geocell reinforced sand supporting strip footing Madhavi Latha and Somwanshi [66] ECA with Duncan-Chang model 3-D/FLAC Geocell reinforced sand supporting a square footing Saride et al....
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TL;DR: In this article, a series of model tests has been carried out to develop an understanding of the influence of the geocell material on the load-carrying mechanism of the reinforced sand foundations under strip loading.
Abstract: In this study, a series of model tests has been carried out to develop an understanding of the influence of the geocell material on the load-carrying mechanism of the geocell-reinforced sand foundations under strip loading. Geocells of different types were prepared using geogrids of different types. The parameters studied are as follows: the footing load-settlement response, deformation on the fill surface, strain in the geocell, pressure transmitted to the subgrade soil underlying the geocell mattress, and load dispersion in the geocell mattress. The test results indicate that the strength, stiffness, aperture opening size, and orientation of the rib of the geocell material influence the performance of the reinforced-sand foundation bed. Geocells made of geogrids of higher strength, relatively smaller size aperture opening, and ribs of orthogonal orientation give better performance improvement.
71 citations
TL;DR: In this article, a method for predicting the bearing capacity of geocell-reinforced soils, taking into account the soil foundation bearing capacity and the geocell reinforcement mechanisms, is presented.
Abstract: Geocell geosynthetics have been used in several areas of geotechnical engineering, such as retaining walls, slope protection against erosion, road bases and channel lining. However, geocell was initially designed to improve soil bearing capacity. Performing works in soft soils is always a challenge to geotechnical engineering and involves risks, such as (global and local) soil failures and large settlements. As reinforcement, geocell satisfactorily increases the bearing capacity of the soil, enabling its use. In this regard, this paper presents a method for predicting the bearing capacity of geocell-reinforced soils, taking into account the soil foundation bearing capacity and the geocell reinforcement mechanisms – the stress dispersion effect and the confinement effect. The proposed method is verified with the results of laboratory experiments by several researchers and compared with other calculation methods. The results show that the calculated bearing capacity obtained by this method give a ...
56 citations
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TL;DR: In this article, a simple, practical procedure for representing the nonlinear, stress-dependent, inelastic stress-strain behavior of soils was developed, based on the results of standard triaxial tests on plane strain compression tests involving primary loading, unloading, and reloading.
Abstract: A simple, practical procedure for representing the nonlinear, stress-dependent, inelastic stress-strain behavior of soils was developed. The values of the required parameters employed in the stress-strain relationship may be derived from the results of standard triaxial tests on plane strain compression tests involving primary loading, unloading, and reloading. Comparisons of calculated and measured strains in specimens of dense and loose silica sand showed that the relationship was capable of accurately representing the behavior of this sand under complex triaxial loading conditions, and analyses of the behavior of footings on sand and clay showed that finite element stress analyses conducted using this relationship were in good agreement with empirical observations and applicable theories.
1,982 citations
TL;DR: In this article, the authors present the results from laboratory-model tests on a strip footing supported by a sand bed reinforced with a geocell mattress and show that 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.
Abstract: 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.
280 citations
TL;DR: In this article, the effectiveness of geocell reinforcement placed in the granular fill overlying soft clay beds has been studied by small-scale model tests in the laboratory, where the influence of width and height of the geocell mattress as well as that of a planar geogrid layer at the base of the mattress on the overall performance of the system has been systematically studied through a series of tests.
Abstract: The effectiveness of geocell reinforcement placed in the granular fill overlying soft clay beds has been studied by small-scale model tests in the laboratory. The test beds were subjected to monotonic loading by a rigid circular footing. Footing load, footing settlement and deformations on the fill surface were measured during the tests. The influence of width and height of geocell mattress as well as that of a planar geogrid layer at the base of the geocell mattress on the overall performance of the system has been systematically studied through a series of tests. The test results indicate that with the provision of geocell reinforcement in the overlying sand layer, a substantial performance improvement can be obtained in terms of increase in the load carrying capacity and reduction in surface heaving of the foundation bed. An additional layer of geogrid placed at the base of the geocell mattress further enhances the load carrying capacity and stiffness of the foundation bed. Its beneficial effect decreases with the increase in the height of the geocell mattress. A seven-fold increase in the bearing capacity of the circular footing can be obtained by providing geocell reinforcement along with a basal geogrid layer in the sand bed underlying soft clay.
236 citations
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 effects of reinforcement form on strength improvement of geosynthetic-reinforced sand through triaxial compression tests were analyzed to understand the strength improvement due to reinforcement in different forms.
Abstract: This paper studies the effects of reinforcement form on strength improvement of geosynthetic-reinforced sand through triaxial compression tests. Samples of sand reinforced with geosynthetics in three different forms, viz. horizontal layers, geocells, and randomly distributed discrete fibers are tested in triaxial compression and results are analyzed to understand the strength improvement in sand due to reinforcement in different forms. Three types of geosynthetics—geotextile, geogrid, and polyester film are used for reinforcing sand in layer form. Two types of geosynthetics—geotextile and polyester film are used in tests on geocells. Polyester film is used in all the three forms of reinforcement viz. planar, cellular, and discrete fiber reinforcement. Among the three forms of reinforcement, cellular form of reinforcement is found to be more effective in improving the strength. The discrete fiber form of reinforcement used in the studies is found to be inferior compared to the other two forms. The scale effects involved in the results obtained from the triaxial tests on small size samples of reinforced sand are discussed and the qualitative importance of the results is demonstrated through comparisons with theoretical computations.
209 citations