This paper presents the results of the laboratory model tests and the numerical studies conducted... more This paper presents the results of the laboratory model tests and the numerical studies conducted on small diameter PVC pipes, buried in geocell reinforced sand beds. The aim of the study was to evaluate the suitability of the geocell reinforcement in protecting the underground utilities and buried pipelines. In addition to geocells, the efficacy of only geogrid and geocell with additional basal geogrid cases were also studied. A PVC (Poly Vinyl Chloride) pipe with external diameter 75 mm and thickness 1.4 mm was used in the experiments. The vehicle tire contact pressure was simulated by applying the pressure on the top of the bed with the help of a steel plate. Results suggest that the use of geocells with additional basal geogrid considerably reduces the deformation of the pipe as compared to other types of reinforcements. Further, the depth of placement of pipe was also varied between 1B to 2B (B is the width of loading plate) below the plate in the presence of geocell with additional basal geogrid. More than 50% reduction in the pressure and more than 40% reduction in the strain values were observed in the presence of reinforcements at different depths as compared to the unreinforced beds. Conversely, the performance of the subgrade soil was also found to be marginally influenced by the position of the pipe, even in the presence of the relatively stiff reinforcement system. Further, experimental results were validated with 3-dimensional numerical studies using FLAC 3D (Fast Lagrangian Analysis of Continua in 3D). A good agreement in the measured pipe stain values were observed between the experimental and numerical studies. Numerical studies revealed that the geocells distribute the stresses in the lateral direction and thus reduce the pressure on the pipe. In addition, the results of the 1-g model tests were scaled up to the prototype case of the shallow buried pipeline below the pavement using the appropriate scaling laws.
Numerical modelling of the geocell has been always a big challenge due to its complex honeycomb
... more Numerical modelling of the geocell has been always a big challenge due to its complex honeycomb
structure. Generally, the equivalent composite approach is adopted to model the geocells. In equivalent
composite approach, the geocell-soil composite is treated as the soil layer with improved strength and
stiffness values. Though this approach is very simple, it is unrealistic to model geocells as the soil layer.
This paper presents a more realistic modelling approach to model geocells in 3-dimensional (3D)
framework. Numerical simulations have been carried by forming the actual 3D honeycomb shape of the
geocells using the finite difference package FLAC
3D
(Fast Lagrangian Analysis of Continua in 3D). Geocells
are modelled using the geogrid structural element available in the FLAC
3D
with the inclusion of the
interface element. In addition to the modelling of geocells, other two cases, namely, only geogrid and
geocell with additional basal geogrid cases were also modelled. It was found that the geocells distribute
the load laterally and to a relatively shallow depth as compared to unreinforced case and the geogrid
reinforced case. The numerical model was also validated with the experimental studies and the results
are found to be in good agreement with each other. The validated numerical model was used to study the
influence of various properties of the geocells on the performance of the reinforced foundation beds. The
performance of the foundation bed was directly influenced by the modulus and the height of the geo-
cells. Similarly, the pocket size of the geocell inversely affected the performance of the reinforced beds.
The geocell with textured surface yielded better performance than the geocell with smooth surface.
Due to its complex honeycomb structure, the numerical modeling of the geocell has always been a b... more Due to its complex honeycomb structure, the numerical modeling of the geocell has always been a big challenge. Generally, the equivalent composite approach is used to model the geocells. In the equivalent composite approach, the geocellsoil composite is treated as the soil layer with improved strength and stiffness values. Though this approach is very simple, it is unrealistic to model the geocells as the soil layer. This paper presents a more realistic approach of modeling the geocells in three-dimensional (3D) framework by considering the actual curvature of the geocell pocket. A square footing resting on geocell reinforced soft clay bed was modeled using the "fast Lagrangian analysis of continua in 3D" (FLAC 3D ) finite difference package. Three different material models, namely modified Cam-clay, Mohr-Coulomb, and linear elastic were used to simulate the behaviour of foundation soil, infill soil and the geocell, respectively. It was found that the geocells distribute the load laterally to the wider area below the footing as compared to the unreinforced case. More than 50% reduction in the stress was observed in the clay bed in the presence of geocells. In addition to geocells, two other cases, namely, only geogrid and geocell with additional basal geogrid cases were also simulated. The numerical model was systematically validated with the results of the physical model tests. Using the validated numerical model, parametric studies were conducted to evaluate the influence of various geocell properties on the performance of reinforced clay beds.
Geotechnical Special Publications-238, ASCE, 289-298. , 2014
This paper describes the laboratory tests on small diameter PVC ((Poly Vinyl Chloride) pipes b... more This paper describes the laboratory tests on small diameter PVC ((Poly Vinyl Chloride) pipes buried in unreinforced and geosynthetic reinforced sand subjected to static loading. The aim of the study was to evaluate the appropriateness
of the combination of geocell and geogrid reinforcement system in protecting the underground utilities and buried pipelines. A pipe with external diameter of 75 mm
and thickness of 1.4 mm was placed below the footing at different depths ranging from 1B to 2B (B is the width of the footing). Commercially available Neoweb geocells and biaxial geogrids (SS-20) were used as the reinforcements. Results indicate that the use of combination of geocell and the geogrid reinforcement system
considerably reduces the deformation of the pipe as compared to unreinforced bed. Above 50% reduction in the pressure and more than 40% reduction in the strain
values were observed in the reinforced bed as compared to the unreinforced bed at
different depths. Conversely, the performance of the foundation bed was also found to be marginally influenced by the position of the pipe, even in the presence of the
relatively stiff reinforcement system.
International Journal of Geosynthetics and Ground Engineering. 1(2),1-13, 2015
This manuscript deals with the experimental and analytical studies carried out to explore the pos... more This manuscript deals with the experimental and analytical studies carried out to explore the possibility of using naturally available bamboo to increase the bearing capacity of the soft soil. In order to extract the additional confinement effect on the soil, 3 dimensional-cells are formed from the locally available bamboo known as bamboo cells. The performances of the bamboo cells are compared with the commercial geocells. Further, a planar reinforcement in the form of bamboo grid was provided at the base of bamboo cells and the performance was compared with the clay bed reinforced with the combination of geocell and geogrid. The results of the laboratory plate load tests suggested that the ultimate bearing capacity of the clay bed reinforced with combination of bamboo cell and bamboo grid was about 1.3 times higher than the geocell and geogrid reinforced clay beds. In addition, a substantial reduction in the settlement was also observed. An analytical model was also proposed to estimate the bearing capacity of the clay bed reinforced with bamboo cells and bamboo grids. The model comprised of three mechanisms, namely the lateral resistance effect, vertical stress dispersion effect and membrane effect. The results predicted from the analytical model were found to be in good agreement with the experimental results. In a larger perspective, this study proposes a cost effective ground improvement technique in soft soils as an alternative to geocells and geogrids.
Proceedings of Indian Geotechnical Conference-2012, New Delhi. 536-539. , 2012
This paper summarizes the beneficial effect of geocell reinforcement in soft clay beds through 1-... more This paper summarizes the beneficial effect of geocell reinforcement in soft clay beds through 1-g model plate load tests and numerical simulations using FLAC 2D . New commercially available PRS Neoweb geocells are used in the investigation; which is known for its high strength and durability. Results show that provision of geocell increases the load carrying capacity of soft clay bed by 5 times. The overall performance of the clay bed improves further due to the provision of planar geogrid at the base of the geocell. Numerical results are also in the same line with the experimental findings.
ABSTRACT Earthquakes are known to have occurred in India from ancient times. More than 50 % of th... more ABSTRACT Earthquakes are known to have occurred in India from ancient times. More than 50 % of the country is vulnerable to earthquakes and it has a coastline of 7,517 km, which implies towards high risk of seismic hazards like liquefaction. Seismic liquefaction is the process by which saturated, unconsolidated soil or sand is converted into a suspension during an earthquake and its effect on structures and buildings can be devastating. In the present study, an attempt has been made to predict the liquefaction susceptibility of India based on corrected SPT values required to prevent the liquefaction for given return periods. The evaluation of liquefaction potential requires the calculation of two parameters, seismic loading and the soil resistance. In order to consider the worst scenario for liquefaction, the water table was assumed at the ground surface. In most of the studies, the seismic loading will be evaluated based on probabilistic methods and the evaluation of soil resistance will be done based on deterministic analysis. In this study an attempt was made to predict the corrected SPT values required to prevent the liquefaction, using probabilistic performance based approach. The contour curves showing the spatial variation of SPT values required to prevent the liquefaction at 3 m depth, for return periods of 475 and 2,500 years are presented in the paper.
Improper disposal of solid waste has resulted in the formation of large number of waste dumps aro... more Improper disposal of solid waste has resulted in the formation of large number of waste dumps around most towns and cities. Improper waste management can lead to serious environmental and health hazard. Also these sites are being used for various infrastructural development around the expanding cites to meet the demand for growing needs. The compressibility and shear strength of the dump sites assume importance in reclamation of waste dumps. The shear strength parameters depend on various factors such as age, composition and moisture content of waste. This paper describes a comprehensive laboratory study performed to investigate the compressibility and shear strength properties of more than10-years-old municipal solid waste (MSW) dump site around Bangalore city in India. Particle sizes analysis has shown that about 75% of waste contained particles are coarser than 4.75 mm and 88% of particles were coarser more than 2.36 mm. Standard Proctor compaction tests yielded a maximum dry density of 9.28kN/m3 at 42.8% optimum moisture content for dumped MSW. Consolidation and shear tests were conducted on samples containing size fraction in the range of 4.75 to 0.15 mm and compacted to Proctor’s maximum dry density at optimum water content. Compression ratio val-ue was found to be 0.105. Based on direct shear tests, the friction angle was found to be 25.6 degrees and cohesion was about 10 kPa. Most dump sites are not directly suitable for civil in-frastructure requirements.
Proceedings of the 8th International Conference (BCR2A'09), June 29 - July 2 2009, Unversity of Illinois at Urbana - Champaign, Champaign, Illinois, USA, 2009
This study describes two machine learning techniques applied to predict liquefaction susceptibili... more This study describes two machine learning techniques applied to predict liquefaction susceptibility of soil based on the standard penetration test (SPT) data from the 1999 Chi-Chi, Taiwan earthquake. The first machine learning technique which uses Artificial Neural Network (ANN) based on multi-layer perceptions (MLP) that are trained with Levenberg-Marquardt backpropagation algorithm. The second machine learning technique uses the Support Vector machine (SVM) that is firmly based on the theory of statistical learning theory, uses classification technique. ANN and SVM have been developed to predict liquefaction susceptibility using corrected SPT [(N 1 ) 60 ] and cyclic stress ratio (CSR). Further, an attempt has been made to simplify the models, requiring only the two parameters [(N 1 ) 60 and peck ground acceleration (a max /g)], for the prediction of liquefaction susceptibility. The developed ANN and SVM models have also been applied to different case histories available globally. The paper also highlights the capability of the SVM over the ANN models.
In this paper an attempt has been made to evaluate the spatial variability of the depth of weathe... more In this paper an attempt has been made to evaluate the spatial variability of the depth of weathered and engineering bedrock in Bangalore, south India using Multichannel Analysis of Surface Wave (MASW) survey. One-dimensional MASW survey has been carried out at 58 locations and shear-wave velocities are measured. Using velocity profiles, the depth of weathered rock and engineering rock surface levels has been determined. Based on the literature, shear-wave velocity of 330 ± 30 m/s for weathered rock or soft rock and 760 ± 60 m/s for engineering rock or hard rock has been considered. Depths corresponding to these velocity ranges are evaluated with respect to ground contour levels and top surface levels have been mapped with an interpolation technique using natural neighborhood. The depth of weathered rock varies from 1 m to about 21 m. In 58 testing locations, only 42 locations reached the depths which have a shear-wave velocity of more than 760 ± 60 m/s. The depth of engineering rock is evaluated from these data and it varies from 1 m to about 50 m. Further, these rock depths have been compared with a subsurface profile obtained from a twodimensional (2-D) MASW survey at 20 locations and a few selected available bore logs from the deep geotechnical boreholes.
This paper presents the results of the laboratory model tests and the numerical studies conducted... more This paper presents the results of the laboratory model tests and the numerical studies conducted on small diameter PVC pipes, buried in geocell reinforced sand beds. The aim of the study was to evaluate the suitability of the geocell reinforcement in protecting the underground utilities and buried pipelines. In addition to geocells, the efficacy of only geogrid and geocell with additional basal geogrid cases were also studied. A PVC (Poly Vinyl Chloride) pipe with external diameter 75 mm and thickness 1.4 mm was used in the experiments. The vehicle tire contact pressure was simulated by applying the pressure on the top of the bed with the help of a steel plate. Results suggest that the use of geocells with additional basal geogrid considerably reduces the deformation of the pipe as compared to other types of reinforcements. Further, the depth of placement of pipe was also varied between 1B to 2B (B is the width of loading plate) below the plate in the presence of geocell with additional basal geogrid. More than 50% reduction in the pressure and more than 40% reduction in the strain values were observed in the presence of reinforcements at different depths as compared to the unreinforced beds. Conversely, the performance of the subgrade soil was also found to be marginally influenced by the position of the pipe, even in the presence of the relatively stiff reinforcement system. Further, experimental results were validated with 3-dimensional numerical studies using FLAC 3D (Fast Lagrangian Analysis of Continua in 3D). A good agreement in the measured pipe stain values were observed between the experimental and numerical studies. Numerical studies revealed that the geocells distribute the stresses in the lateral direction and thus reduce the pressure on the pipe. In addition, the results of the 1-g model tests were scaled up to the prototype case of the shallow buried pipeline below the pavement using the appropriate scaling laws.
Numerical modelling of the geocell has been always a big challenge due to its complex honeycomb
... more Numerical modelling of the geocell has been always a big challenge due to its complex honeycomb
structure. Generally, the equivalent composite approach is adopted to model the geocells. In equivalent
composite approach, the geocell-soil composite is treated as the soil layer with improved strength and
stiffness values. Though this approach is very simple, it is unrealistic to model geocells as the soil layer.
This paper presents a more realistic modelling approach to model geocells in 3-dimensional (3D)
framework. Numerical simulations have been carried by forming the actual 3D honeycomb shape of the
geocells using the finite difference package FLAC
3D
(Fast Lagrangian Analysis of Continua in 3D). Geocells
are modelled using the geogrid structural element available in the FLAC
3D
with the inclusion of the
interface element. In addition to the modelling of geocells, other two cases, namely, only geogrid and
geocell with additional basal geogrid cases were also modelled. It was found that the geocells distribute
the load laterally and to a relatively shallow depth as compared to unreinforced case and the geogrid
reinforced case. The numerical model was also validated with the experimental studies and the results
are found to be in good agreement with each other. The validated numerical model was used to study the
influence of various properties of the geocells on the performance of the reinforced foundation beds. The
performance of the foundation bed was directly influenced by the modulus and the height of the geo-
cells. Similarly, the pocket size of the geocell inversely affected the performance of the reinforced beds.
The geocell with textured surface yielded better performance than the geocell with smooth surface.
Due to its complex honeycomb structure, the numerical modeling of the geocell has always been a b... more Due to its complex honeycomb structure, the numerical modeling of the geocell has always been a big challenge. Generally, the equivalent composite approach is used to model the geocells. In the equivalent composite approach, the geocellsoil composite is treated as the soil layer with improved strength and stiffness values. Though this approach is very simple, it is unrealistic to model the geocells as the soil layer. This paper presents a more realistic approach of modeling the geocells in three-dimensional (3D) framework by considering the actual curvature of the geocell pocket. A square footing resting on geocell reinforced soft clay bed was modeled using the "fast Lagrangian analysis of continua in 3D" (FLAC 3D ) finite difference package. Three different material models, namely modified Cam-clay, Mohr-Coulomb, and linear elastic were used to simulate the behaviour of foundation soil, infill soil and the geocell, respectively. It was found that the geocells distribute the load laterally to the wider area below the footing as compared to the unreinforced case. More than 50% reduction in the stress was observed in the clay bed in the presence of geocells. In addition to geocells, two other cases, namely, only geogrid and geocell with additional basal geogrid cases were also simulated. The numerical model was systematically validated with the results of the physical model tests. Using the validated numerical model, parametric studies were conducted to evaluate the influence of various geocell properties on the performance of reinforced clay beds.
Geotechnical Special Publications-238, ASCE, 289-298. , 2014
This paper describes the laboratory tests on small diameter PVC ((Poly Vinyl Chloride) pipes b... more This paper describes the laboratory tests on small diameter PVC ((Poly Vinyl Chloride) pipes buried in unreinforced and geosynthetic reinforced sand subjected to static loading. The aim of the study was to evaluate the appropriateness
of the combination of geocell and geogrid reinforcement system in protecting the underground utilities and buried pipelines. A pipe with external diameter of 75 mm
and thickness of 1.4 mm was placed below the footing at different depths ranging from 1B to 2B (B is the width of the footing). Commercially available Neoweb geocells and biaxial geogrids (SS-20) were used as the reinforcements. Results indicate that the use of combination of geocell and the geogrid reinforcement system
considerably reduces the deformation of the pipe as compared to unreinforced bed. Above 50% reduction in the pressure and more than 40% reduction in the strain
values were observed in the reinforced bed as compared to the unreinforced bed at
different depths. Conversely, the performance of the foundation bed was also found to be marginally influenced by the position of the pipe, even in the presence of the
relatively stiff reinforcement system.
International Journal of Geosynthetics and Ground Engineering. 1(2),1-13, 2015
This manuscript deals with the experimental and analytical studies carried out to explore the pos... more This manuscript deals with the experimental and analytical studies carried out to explore the possibility of using naturally available bamboo to increase the bearing capacity of the soft soil. In order to extract the additional confinement effect on the soil, 3 dimensional-cells are formed from the locally available bamboo known as bamboo cells. The performances of the bamboo cells are compared with the commercial geocells. Further, a planar reinforcement in the form of bamboo grid was provided at the base of bamboo cells and the performance was compared with the clay bed reinforced with the combination of geocell and geogrid. The results of the laboratory plate load tests suggested that the ultimate bearing capacity of the clay bed reinforced with combination of bamboo cell and bamboo grid was about 1.3 times higher than the geocell and geogrid reinforced clay beds. In addition, a substantial reduction in the settlement was also observed. An analytical model was also proposed to estimate the bearing capacity of the clay bed reinforced with bamboo cells and bamboo grids. The model comprised of three mechanisms, namely the lateral resistance effect, vertical stress dispersion effect and membrane effect. The results predicted from the analytical model were found to be in good agreement with the experimental results. In a larger perspective, this study proposes a cost effective ground improvement technique in soft soils as an alternative to geocells and geogrids.
Proceedings of Indian Geotechnical Conference-2012, New Delhi. 536-539. , 2012
This paper summarizes the beneficial effect of geocell reinforcement in soft clay beds through 1-... more This paper summarizes the beneficial effect of geocell reinforcement in soft clay beds through 1-g model plate load tests and numerical simulations using FLAC 2D . New commercially available PRS Neoweb geocells are used in the investigation; which is known for its high strength and durability. Results show that provision of geocell increases the load carrying capacity of soft clay bed by 5 times. The overall performance of the clay bed improves further due to the provision of planar geogrid at the base of the geocell. Numerical results are also in the same line with the experimental findings.
ABSTRACT Earthquakes are known to have occurred in India from ancient times. More than 50 % of th... more ABSTRACT Earthquakes are known to have occurred in India from ancient times. More than 50 % of the country is vulnerable to earthquakes and it has a coastline of 7,517 km, which implies towards high risk of seismic hazards like liquefaction. Seismic liquefaction is the process by which saturated, unconsolidated soil or sand is converted into a suspension during an earthquake and its effect on structures and buildings can be devastating. In the present study, an attempt has been made to predict the liquefaction susceptibility of India based on corrected SPT values required to prevent the liquefaction for given return periods. The evaluation of liquefaction potential requires the calculation of two parameters, seismic loading and the soil resistance. In order to consider the worst scenario for liquefaction, the water table was assumed at the ground surface. In most of the studies, the seismic loading will be evaluated based on probabilistic methods and the evaluation of soil resistance will be done based on deterministic analysis. In this study an attempt was made to predict the corrected SPT values required to prevent the liquefaction, using probabilistic performance based approach. The contour curves showing the spatial variation of SPT values required to prevent the liquefaction at 3 m depth, for return periods of 475 and 2,500 years are presented in the paper.
Improper disposal of solid waste has resulted in the formation of large number of waste dumps aro... more Improper disposal of solid waste has resulted in the formation of large number of waste dumps around most towns and cities. Improper waste management can lead to serious environmental and health hazard. Also these sites are being used for various infrastructural development around the expanding cites to meet the demand for growing needs. The compressibility and shear strength of the dump sites assume importance in reclamation of waste dumps. The shear strength parameters depend on various factors such as age, composition and moisture content of waste. This paper describes a comprehensive laboratory study performed to investigate the compressibility and shear strength properties of more than10-years-old municipal solid waste (MSW) dump site around Bangalore city in India. Particle sizes analysis has shown that about 75% of waste contained particles are coarser than 4.75 mm and 88% of particles were coarser more than 2.36 mm. Standard Proctor compaction tests yielded a maximum dry density of 9.28kN/m3 at 42.8% optimum moisture content for dumped MSW. Consolidation and shear tests were conducted on samples containing size fraction in the range of 4.75 to 0.15 mm and compacted to Proctor’s maximum dry density at optimum water content. Compression ratio val-ue was found to be 0.105. Based on direct shear tests, the friction angle was found to be 25.6 degrees and cohesion was about 10 kPa. Most dump sites are not directly suitable for civil in-frastructure requirements.
Proceedings of the 8th International Conference (BCR2A'09), June 29 - July 2 2009, Unversity of Illinois at Urbana - Champaign, Champaign, Illinois, USA, 2009
This study describes two machine learning techniques applied to predict liquefaction susceptibili... more This study describes two machine learning techniques applied to predict liquefaction susceptibility of soil based on the standard penetration test (SPT) data from the 1999 Chi-Chi, Taiwan earthquake. The first machine learning technique which uses Artificial Neural Network (ANN) based on multi-layer perceptions (MLP) that are trained with Levenberg-Marquardt backpropagation algorithm. The second machine learning technique uses the Support Vector machine (SVM) that is firmly based on the theory of statistical learning theory, uses classification technique. ANN and SVM have been developed to predict liquefaction susceptibility using corrected SPT [(N 1 ) 60 ] and cyclic stress ratio (CSR). Further, an attempt has been made to simplify the models, requiring only the two parameters [(N 1 ) 60 and peck ground acceleration (a max /g)], for the prediction of liquefaction susceptibility. The developed ANN and SVM models have also been applied to different case histories available globally. The paper also highlights the capability of the SVM over the ANN models.
In this paper an attempt has been made to evaluate the spatial variability of the depth of weathe... more In this paper an attempt has been made to evaluate the spatial variability of the depth of weathered and engineering bedrock in Bangalore, south India using Multichannel Analysis of Surface Wave (MASW) survey. One-dimensional MASW survey has been carried out at 58 locations and shear-wave velocities are measured. Using velocity profiles, the depth of weathered rock and engineering rock surface levels has been determined. Based on the literature, shear-wave velocity of 330 ± 30 m/s for weathered rock or soft rock and 760 ± 60 m/s for engineering rock or hard rock has been considered. Depths corresponding to these velocity ranges are evaluated with respect to ground contour levels and top surface levels have been mapped with an interpolation technique using natural neighborhood. The depth of weathered rock varies from 1 m to about 21 m. In 58 testing locations, only 42 locations reached the depths which have a shear-wave velocity of more than 760 ± 60 m/s. The depth of engineering rock is evaluated from these data and it varies from 1 m to about 50 m. Further, these rock depths have been compared with a subsurface profile obtained from a twodimensional (2-D) MASW survey at 20 locations and a few selected available bore logs from the deep geotechnical boreholes.
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Papers by T. G. Sitharam
structure. Generally, the equivalent composite approach is adopted to model the geocells. In equivalent
composite approach, the geocell-soil composite is treated as the soil layer with improved strength and
stiffness values. Though this approach is very simple, it is unrealistic to model geocells as the soil layer.
This paper presents a more realistic modelling approach to model geocells in 3-dimensional (3D)
framework. Numerical simulations have been carried by forming the actual 3D honeycomb shape of the
geocells using the finite difference package FLAC
3D
(Fast Lagrangian Analysis of Continua in 3D). Geocells
are modelled using the geogrid structural element available in the FLAC
3D
with the inclusion of the
interface element. In addition to the modelling of geocells, other two cases, namely, only geogrid and
geocell with additional basal geogrid cases were also modelled. It was found that the geocells distribute
the load laterally and to a relatively shallow depth as compared to unreinforced case and the geogrid
reinforced case. The numerical model was also validated with the experimental studies and the results
are found to be in good agreement with each other. The validated numerical model was used to study the
influence of various properties of the geocells on the performance of the reinforced foundation beds. The
performance of the foundation bed was directly influenced by the modulus and the height of the geo-
cells. Similarly, the pocket size of the geocell inversely affected the performance of the reinforced beds.
The geocell with textured surface yielded better performance than the geocell with smooth surface.
of the combination of geocell and geogrid reinforcement system in protecting the underground utilities and buried pipelines. A pipe with external diameter of 75 mm
and thickness of 1.4 mm was placed below the footing at different depths ranging from 1B to 2B (B is the width of the footing). Commercially available Neoweb geocells and biaxial geogrids (SS-20) were used as the reinforcements. Results indicate that the use of combination of geocell and the geogrid reinforcement system
considerably reduces the deformation of the pipe as compared to unreinforced bed. Above 50% reduction in the pressure and more than 40% reduction in the strain
values were observed in the reinforced bed as compared to the unreinforced bed at
different depths. Conversely, the performance of the foundation bed was also found to be marginally influenced by the position of the pipe, even in the presence of the
relatively stiff reinforcement system.
structure. Generally, the equivalent composite approach is adopted to model the geocells. In equivalent
composite approach, the geocell-soil composite is treated as the soil layer with improved strength and
stiffness values. Though this approach is very simple, it is unrealistic to model geocells as the soil layer.
This paper presents a more realistic modelling approach to model geocells in 3-dimensional (3D)
framework. Numerical simulations have been carried by forming the actual 3D honeycomb shape of the
geocells using the finite difference package FLAC
3D
(Fast Lagrangian Analysis of Continua in 3D). Geocells
are modelled using the geogrid structural element available in the FLAC
3D
with the inclusion of the
interface element. In addition to the modelling of geocells, other two cases, namely, only geogrid and
geocell with additional basal geogrid cases were also modelled. It was found that the geocells distribute
the load laterally and to a relatively shallow depth as compared to unreinforced case and the geogrid
reinforced case. The numerical model was also validated with the experimental studies and the results
are found to be in good agreement with each other. The validated numerical model was used to study the
influence of various properties of the geocells on the performance of the reinforced foundation beds. The
performance of the foundation bed was directly influenced by the modulus and the height of the geo-
cells. Similarly, the pocket size of the geocell inversely affected the performance of the reinforced beds.
The geocell with textured surface yielded better performance than the geocell with smooth surface.
of the combination of geocell and geogrid reinforcement system in protecting the underground utilities and buried pipelines. A pipe with external diameter of 75 mm
and thickness of 1.4 mm was placed below the footing at different depths ranging from 1B to 2B (B is the width of the footing). Commercially available Neoweb geocells and biaxial geogrids (SS-20) were used as the reinforcements. Results indicate that the use of combination of geocell and the geogrid reinforcement system
considerably reduces the deformation of the pipe as compared to unreinforced bed. Above 50% reduction in the pressure and more than 40% reduction in the strain
values were observed in the reinforced bed as compared to the unreinforced bed at
different depths. Conversely, the performance of the foundation bed was also found to be marginally influenced by the position of the pipe, even in the presence of the
relatively stiff reinforcement system.