Ennio Palmeira - Academia.edu (original) (raw)

Papers by Ennio Palmeira

Research paper thumbnail of Influence de la nature de la bentonite sur la transmissivité d'interface géomembrane-géosynthétique bentonitique

HAL (Le Centre pour la Communication Scientifique Directe), Jun 18, 2009

Research paper thumbnail of Caractérisation de la perméabilité au gaz des GSB en conditions non saturées

International audienceThis paper is a contribution to the characterization of permeability to gas... more International audienceThis paper is a contribution to the characterization of permeability to gas of unsaturated GCLs, with applications in cover liners of municipal solid waste landfills. Conducting such tests at low gas pressure gradient limits the risk of moisture distribution change in the bentonite, which has been observed under high pressure gradients. However, a consequence of a low pressure gradient is a small gas flow rate that is difficult to measure with good accuracy. Therefore, a solution may be the use of transient state tests, like the falling pressure test adapted to GCLs permeability characterization. This paper shows the influence of the main parameters related to the test and to the material tested (natural or activated calcium bentonite, moisture content, presence or not of small cracks in the bentonite). The results obtained showed good repeatability for gas differential pressures up to 40 kPa for the test conditions employed in this work. The results showed tha...

Research paper thumbnail of Numerical Analysis of Unpaved Roads Subjected to Surface Maintenance

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2022

Geosynthetics have proven to be beneficial in reinforcing soils, especially in problems with larg... more Geosynthetics have proven to be beneficial in reinforcing soils, especially in problems with large deformations, such as unpaved roads built on soft soils and subjected to high loads. Due to heavy machinery traffic, this situation occurs even during the construction period of the road, in which is necessary to perform surface maintenance to the execution of the fill layers. Several experimental studies have indicated an improvement in the mechanical performance of unpaved roads when subjected to surface maintenance. The present research aimed at numerically investigate the behavior of unreinforced and reinforced unpaved roads subjected to surface maintenance. The analyses consisted of the following steps: determination of geostatic stresses in the subgrade; inclusion of the fill layer, as well as the geosynthetic reinforcement at the interface between the materials; application of a distributed load on the fill; unloading; execution of the surface maintenance from the deformed configuration of the fill; and reapplication of the load. The results indicate that the mechanical behavior of these roads will be better represented by the sequence described. Furthermore, relevant information on loads in the reinforcement and influence of material properties were obtained.

Research paper thumbnail of Simulation of Explosions of Pressurised Pipes in Geosynthetic Reinforced Embankments

Slopes and Retaining Structures Under Seismic and Static Conditions, 2005

This paper presents the results of a study on the use of geosynthetic reinforced embankments for ... more This paper presents the results of a study on the use of geosynthetic reinforced embankments for the protection of buried pressurised pipes by means of laboratory tests. The expansion of a pipe inside reinforced and unreinforced sand was simulated in models studies in the laboratory using a large rigid steel tank. Different types and configurations of geosynthetics were tested including woven geotextiles, geogrids and metallic reinforcements. The scale of the models in the laboratory was 1:5 and the series of the tests involved a continuous expansion of the pipe walls (thin rubber membrane) until failure of the soil mass was achieved. The results obtained showed a significant influence of the presence of the reinforcement on the pressure in the pipe, depending on reinforcement type and arrangement, and the potential use of reinforced embankments to protect pressurized pipes.

Research paper thumbnail of Bearing force mobilisation in pull-out tests on geogrids

Geotextiles and Geomembranes, 2004

... Bearing force mobilisation in pull-out tests on geogrids. Ennio Marques Palmeira Correspondin... more ... Bearing force mobilisation in pull-out tests on geogrids. Ennio Marques Palmeira Corresponding Author Contact Information , E-mail The Corresponding Author. Department of Civil and Environmental Engineering-FT, University of Brasilia, 70910-900, Brasilia, DF, Brazil. ...

Research paper thumbnail of A study of the mechanics of unpaved roads with reference to the effects of surface maintenance

Geotextiles and Geomembranes, 1993

... Fannin, RJ (1986). Geogrid reinforcement of granular layers on soft clay -- a study at model ... more ... Fannin, RJ (1986). Geogrid reinforcement of granular layers on soft clay -- a study at model and full scale, D.Phil thesis, University of Oxford. Giroud, JP & Noiray, L. (1981). ... Love, JP (1984). Model testing of geogrids in unpaved roads. DPhil thesis, University of Oxford. ...

Research paper thumbnail of Backanalyses of geosynthetic reinforced embankments on soft soils

Geotextiles and Geomembranes, 1998

Geosynthetic reinforcement can be effectively used to increase the factor of safety of embankment... more Geosynthetic reinforcement can be effectively used to increase the factor of safety of embankments on soft soils, particularly for shallow soft foundations layers. Several design approaches can be found in the literature dealing with the design of reinforced embankments on weak subgrades. Unfortunately, only a few well-documented case histories of reinforced embankments which led to failure have been reported. This paper presents backanalyses of some reinforced embankments that can be found in the literature using stability analysis methods commonly employed in routine works. Predicted values of safety factors at failure heights were close to one, and in spite of the limited amount of data available the results obtained suggest that these rather simple methods are useful tools for predicting factors of safety of reinforced embankments when the required input data are available and accurate. Nevertheless, even in these cases the backanalyses of the reinforced embankments suggest the use of factors of safety greater than 1.2 in routine works. 1998 Elsevier Science Ltd.

Research paper thumbnail of Performance of drainage systems incorporating geosynthetics and their effect on leachate properties

Geotextiles and Geomembranes, 2006

Geosynthetics have been increasingly used in drainage systems of waste disposal areas. This paper... more Geosynthetics have been increasingly used in drainage systems of waste disposal areas. This paper presents the performance of four experimental domestic waste cells with drainage systems consisting of sand, gravel, a combination of geotextile and whole tires and a geocomposite for drainage over a period of 5 years. The volumes and variations of physical and chemical characteristics of the leachate with time were assessed. The instrumentation installed in the cells allowed for the measurement of waste settlements and temperature with time. The results obtained show that the type of drainage system may influence some parameters of the leachate but similar behaviours were observed at the end of the monitoring periods. The combination of tires and geotextiles can be a cost-effective drainage solution in regions where traditional materials are scarce or expensive.

Research paper thumbnail of Effectiveness of geogrids as inclusions in cover soils of slopes of waste disposal areas

Geotextiles and Geomembranes, 2003

This paper presents an experimental investigation on the use of geogrids buried in cover soils of... more This paper presents an experimental investigation on the use of geogrids buried in cover soils of slopes of waste disposal areas using a large-scale ramp test. The tests involved the use of geogrids with varying values of tensile stiffness and bearing capacity (number of bearing members) installed at different elevations above the geomembrane resting on the ramp surface. The influence of the use of a geotextile layer on the geomembrane on the behaviour of the system was also assessed. The results show that the presence of a geogrid in the cover soil, and particularly of a geogrid with a geotextile on the geomembrane, can significantly reduce the deformability of the cover soil and the tensile forces mobilised in the geomembrane, as well as increase the inclination of the slope at failure.

Research paper thumbnail of Geosynthetic reinforcement for the reduction of the effects of explosions of internally pressurised buried pipes

Geotextiles and Geomembranes, 2007

Research paper thumbnail of A study on biological clogging of nonwoven geotextiles under leachate flow

Geotextiles and Geomembranes, 2008

This paper presents results of long-term permittivity tests using leachate to evaluate biological... more This paper presents results of long-term permittivity tests using leachate to evaluate biological clogging of nonwoven geotextiles. Three types of geotextiles with varying masses per unit area were used in the tests. The identification and quantification of microorganisms in the geotextile were carried out as well as microscopic investigations. The accuracies of semi-empirical models to evaluate the kinetics of bacteria growth and to correlate hydraulic properties and microbiological parameters were examined. Permittivity tests under increasing water heads were also performed on the geotextile samples already subjected to long-term leachate flow in order to evaluate the values of water heads required to wash the biofilms out of the geotextile pores. The results of the tests showed the marked reduction of geotextile permeability due to biological clogging and that the results of the predictions by semi-empirical methods were consistent with the biological mechanisms observed.

Research paper thumbnail of Tailings-nonwoven geotextile filter compatibility in mining applications

Geotextiles and Geomembranes, 2010

ABSTRACT Nonwoven geotextiles have been commonly used in filtration and drainage of geotechnical ... more ABSTRACT Nonwoven geotextiles have been commonly used in filtration and drainage of geotechnical engineering works. This paper presents a study on the use of such materials in drainage and filtration systems of tailings dams. Different combinations of tailings and geotextiles were submitted to gradient ratio (GR) tests under confinement in the laboratory with varying values of stress levels and hydraulic gradients. The results of GR tests under confining stresses up to 2000kPa are presented and discussed. The dimensions of the tailings particles entrapped in the geotextile specimens and those that piped through the geotextile were also assessed. Geotextile specimens from the drainage system of a tailings dam were exhumed for analyses, as part of the research programme. The results obtained showed that stress levels and the hydraulic gradients used in the tests influenced the behaviour of the system. Physical and microscopic analyses of the specimens tested showed greater geotextile impregnation by tailings particles in the field than in the laboratory. The overall performance of the geotextiles tested under laboratory conditions was satisfactory. However, in the field segregation of tailings particles and transport of fines in suspension can subject the filter to more complex and severe clogging mechanisms, not properly simulated in current standard testing procedures.

Research paper thumbnail of Sagging and filtration behaviour of nonwoven geotextiles overlying different bedding materials

Geotextiles and Geomembranes, 2012

This paper presents and discusses the results obtained in laboratory tests to evaluate sagging an... more This paper presents and discusses the results obtained in laboratory tests to evaluate sagging and filtration behaviour of nonwoven geotextiles overlying particles of different bedding materials. Nonwoven geotextiles with masses per unit area of 200 g/m 2 , 400 g/m 2 and 600 g/m 2 were used in the tests. Stainless steel spheres and gravels were employed as granular materials underlying the geotextile filter. Specific tests to evaluate the intensity of sagging of the geotextile filter in the voids of the underlying material were carried out. Average strains mobilised in the geotextile were assessed in the tests. The grain sizes of the particles that piped through the geotextile filter for different arrangements of spheres as bedding layer for the filter were measured. The results obtained showed that bedding conditions and geotextile structural characteristics can influence its retention capacity. Good comparisons between predicted and measured average geotextile strains were observed.

Research paper thumbnail of Behaviour of a geogrid reinforced wall built with recycled construction and demolition waste backfill on a collapsible foundation

Geotextiles and Geomembranes, 2013

ABSTRACT

Research paper thumbnail of Microstructure and pore characteristics of synthetic filters under confinement

Research paper thumbnail of Characterisation of permeability to gas of geosynthetic clay liners in unsaturated conditions

Geosynthetics International, 2011

This paper is a contribution to the characterisation of permeability to gas of unsaturated GCLs, ... more This paper is a contribution to the characterisation of permeability to gas of unsaturated GCLs, with applications in cover liners of municipal solid waste landfills. Conducting such tests at low gas pressure gradient limits the risk of moisture distribution change in the bentonite, which has been observed under high pressure gradients. However, a consequence of a low pressure gradient is a small gas flow rate that is difficult to measure with good accuracy. Therefore a solution may be the use of transient state tests, such as the falling pressure test adapted to GCL permeability characterisation. This paper shows the influence of the main parameters related to the test, and to the material tested (natural or activated calcium bentonite, moisture content, presence or not of small cracks in the bentonite). The results obtained showed good repeatability for gas differential pressures up to 40 kPa for the test conditions employed in this work. The results showed that the gravimetric moisture content of the GCL necessary to attain a certain permeability value depends on the nature of the bentonite, which was not observed in terms of volumetric moisture content. However, other factors were shown to be more important than the nature of bentonite in GCL permeability to gas: the desiccation due to the gas flow can significantly increase the permeability, which compromises the GCL's performance as a gas barrier.

Research paper thumbnail of Soil–geotextile filter interaction under high stress levels in the gradient ratio test

Geosynthetics International, 2005

ABSTRACT This paper presents the results of gradient ratio tests on different soil - geotextile s... more ABSTRACT This paper presents the results of gradient ratio tests on different soil - geotextile systems under normal stresses up to 2000 kPa. Different types of soil and geotextiles were tested, and the soil particles that passed through the geotextile and those retained in it were collected for particle size analyses. The results obtained show that the use of definitions of gradient ratio based on the measurement of water heads close to the geotextile layer can be useful for a better identification of geotextile-clogging mechanisms. The entrapment of soil particles in the geotextile increases its retaining capacity and alters the conditions for further clogging. The dimensions of the entrapped soil particles can be greater than the geotextile pore dimensions under unconfined conditions and are controlled by soil and geotextile characteristics and by the soil sample preparation technique employed. The results suggest that current retention and permeability criteria for geotextile filters can be excessively conservative. Discussions on geotextile performance in the test and under field conditions are also presented as well as limitations and new proposals for the interpretation of the gradient ratio test.

Research paper thumbnail of Protection of buried pipes against accidental damage using geosynthetics

Geosynthetics International, 2010

ABSTRACT

Research paper thumbnail of Comparisons between predicted and observed behaviour of a geosynthetic reinforced abutment on soft soil

Engineering Geology, 2012

The use of soil reinforcement for the construction of embankments on soft soils has become an inc... more The use of soil reinforcement for the construction of embankments on soft soils has become an increasing practice. This paper presents comparisons between predicted and observed behaviour of a geogrid reinforced abutment on soft soil using a finite element code. The problem is quite complex in terms of geometry and soil conditions. The results obtained in the numerical simulation were compared to the results obtained from instrumentation. The numerical analysis was able to provide good comparisons between calculated and measured vertical displacements and maximum excess pore pressures using back-calculated consolidation properties. However, significant deviations were observed for horizontal displacements and reinforcement forces. Despite some limitations of the numerical tool employed, the results obtained showed that the design could have been improved had such numerical analysis been carried out.

Research paper thumbnail of A study on the behaviour of soil–geotextile systems in filtration tests

Canadian Geotechnical Journal, 1996

The behaviour of soil–geotextile systems in filtration tests is reported for nonwoven geotextiles... more The behaviour of soil–geotextile systems in filtration tests is reported for nonwoven geotextiles under unidirectional flow. A new apparatus was developed to preform filtration tests under an applied vertical stress, and tests were then conducted with different soils and nonwoven geotextiles in order to evaluate the clogging potential and retention capacity of these materials under rather severe combinations of geotextile and soil characteristics. Results show that the geotextiles perfomed well and that observed permeability losses were acceptable even for gradient ratios close to 3. No progressive piping was observed, and it is believed that the retention capacity of the geotextiles may be influenced by their manufacturing process. In general, theoretical predictions for the maximum particle size passing through the geotextile compared well with measurements. Key words: geotextiles, filtration, gradient ratio, permeability, soil retention, clogging.

Research paper thumbnail of Influence de la nature de la bentonite sur la transmissivité d'interface géomembrane-géosynthétique bentonitique

HAL (Le Centre pour la Communication Scientifique Directe), Jun 18, 2009

Research paper thumbnail of Caractérisation de la perméabilité au gaz des GSB en conditions non saturées

International audienceThis paper is a contribution to the characterization of permeability to gas... more International audienceThis paper is a contribution to the characterization of permeability to gas of unsaturated GCLs, with applications in cover liners of municipal solid waste landfills. Conducting such tests at low gas pressure gradient limits the risk of moisture distribution change in the bentonite, which has been observed under high pressure gradients. However, a consequence of a low pressure gradient is a small gas flow rate that is difficult to measure with good accuracy. Therefore, a solution may be the use of transient state tests, like the falling pressure test adapted to GCLs permeability characterization. This paper shows the influence of the main parameters related to the test and to the material tested (natural or activated calcium bentonite, moisture content, presence or not of small cracks in the bentonite). The results obtained showed good repeatability for gas differential pressures up to 40 kPa for the test conditions employed in this work. The results showed tha...

Research paper thumbnail of Numerical Analysis of Unpaved Roads Subjected to Surface Maintenance

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Apr 1, 2022

Geosynthetics have proven to be beneficial in reinforcing soils, especially in problems with larg... more Geosynthetics have proven to be beneficial in reinforcing soils, especially in problems with large deformations, such as unpaved roads built on soft soils and subjected to high loads. Due to heavy machinery traffic, this situation occurs even during the construction period of the road, in which is necessary to perform surface maintenance to the execution of the fill layers. Several experimental studies have indicated an improvement in the mechanical performance of unpaved roads when subjected to surface maintenance. The present research aimed at numerically investigate the behavior of unreinforced and reinforced unpaved roads subjected to surface maintenance. The analyses consisted of the following steps: determination of geostatic stresses in the subgrade; inclusion of the fill layer, as well as the geosynthetic reinforcement at the interface between the materials; application of a distributed load on the fill; unloading; execution of the surface maintenance from the deformed configuration of the fill; and reapplication of the load. The results indicate that the mechanical behavior of these roads will be better represented by the sequence described. Furthermore, relevant information on loads in the reinforcement and influence of material properties were obtained.

Research paper thumbnail of Simulation of Explosions of Pressurised Pipes in Geosynthetic Reinforced Embankments

Slopes and Retaining Structures Under Seismic and Static Conditions, 2005

This paper presents the results of a study on the use of geosynthetic reinforced embankments for ... more This paper presents the results of a study on the use of geosynthetic reinforced embankments for the protection of buried pressurised pipes by means of laboratory tests. The expansion of a pipe inside reinforced and unreinforced sand was simulated in models studies in the laboratory using a large rigid steel tank. Different types and configurations of geosynthetics were tested including woven geotextiles, geogrids and metallic reinforcements. The scale of the models in the laboratory was 1:5 and the series of the tests involved a continuous expansion of the pipe walls (thin rubber membrane) until failure of the soil mass was achieved. The results obtained showed a significant influence of the presence of the reinforcement on the pressure in the pipe, depending on reinforcement type and arrangement, and the potential use of reinforced embankments to protect pressurized pipes.

Research paper thumbnail of Bearing force mobilisation in pull-out tests on geogrids

Geotextiles and Geomembranes, 2004

... Bearing force mobilisation in pull-out tests on geogrids. Ennio Marques Palmeira Correspondin... more ... Bearing force mobilisation in pull-out tests on geogrids. Ennio Marques Palmeira Corresponding Author Contact Information , E-mail The Corresponding Author. Department of Civil and Environmental Engineering-FT, University of Brasilia, 70910-900, Brasilia, DF, Brazil. ...

Research paper thumbnail of A study of the mechanics of unpaved roads with reference to the effects of surface maintenance

Geotextiles and Geomembranes, 1993

... Fannin, RJ (1986). Geogrid reinforcement of granular layers on soft clay -- a study at model ... more ... Fannin, RJ (1986). Geogrid reinforcement of granular layers on soft clay -- a study at model and full scale, D.Phil thesis, University of Oxford. Giroud, JP & Noiray, L. (1981). ... Love, JP (1984). Model testing of geogrids in unpaved roads. DPhil thesis, University of Oxford. ...

Research paper thumbnail of Backanalyses of geosynthetic reinforced embankments on soft soils

Geotextiles and Geomembranes, 1998

Geosynthetic reinforcement can be effectively used to increase the factor of safety of embankment... more Geosynthetic reinforcement can be effectively used to increase the factor of safety of embankments on soft soils, particularly for shallow soft foundations layers. Several design approaches can be found in the literature dealing with the design of reinforced embankments on weak subgrades. Unfortunately, only a few well-documented case histories of reinforced embankments which led to failure have been reported. This paper presents backanalyses of some reinforced embankments that can be found in the literature using stability analysis methods commonly employed in routine works. Predicted values of safety factors at failure heights were close to one, and in spite of the limited amount of data available the results obtained suggest that these rather simple methods are useful tools for predicting factors of safety of reinforced embankments when the required input data are available and accurate. Nevertheless, even in these cases the backanalyses of the reinforced embankments suggest the use of factors of safety greater than 1.2 in routine works. 1998 Elsevier Science Ltd.

Research paper thumbnail of Performance of drainage systems incorporating geosynthetics and their effect on leachate properties

Geotextiles and Geomembranes, 2006

Geosynthetics have been increasingly used in drainage systems of waste disposal areas. This paper... more Geosynthetics have been increasingly used in drainage systems of waste disposal areas. This paper presents the performance of four experimental domestic waste cells with drainage systems consisting of sand, gravel, a combination of geotextile and whole tires and a geocomposite for drainage over a period of 5 years. The volumes and variations of physical and chemical characteristics of the leachate with time were assessed. The instrumentation installed in the cells allowed for the measurement of waste settlements and temperature with time. The results obtained show that the type of drainage system may influence some parameters of the leachate but similar behaviours were observed at the end of the monitoring periods. The combination of tires and geotextiles can be a cost-effective drainage solution in regions where traditional materials are scarce or expensive.

Research paper thumbnail of Effectiveness of geogrids as inclusions in cover soils of slopes of waste disposal areas

Geotextiles and Geomembranes, 2003

This paper presents an experimental investigation on the use of geogrids buried in cover soils of... more This paper presents an experimental investigation on the use of geogrids buried in cover soils of slopes of waste disposal areas using a large-scale ramp test. The tests involved the use of geogrids with varying values of tensile stiffness and bearing capacity (number of bearing members) installed at different elevations above the geomembrane resting on the ramp surface. The influence of the use of a geotextile layer on the geomembrane on the behaviour of the system was also assessed. The results show that the presence of a geogrid in the cover soil, and particularly of a geogrid with a geotextile on the geomembrane, can significantly reduce the deformability of the cover soil and the tensile forces mobilised in the geomembrane, as well as increase the inclination of the slope at failure.

Research paper thumbnail of Geosynthetic reinforcement for the reduction of the effects of explosions of internally pressurised buried pipes

Geotextiles and Geomembranes, 2007

Research paper thumbnail of A study on biological clogging of nonwoven geotextiles under leachate flow

Geotextiles and Geomembranes, 2008

This paper presents results of long-term permittivity tests using leachate to evaluate biological... more This paper presents results of long-term permittivity tests using leachate to evaluate biological clogging of nonwoven geotextiles. Three types of geotextiles with varying masses per unit area were used in the tests. The identification and quantification of microorganisms in the geotextile were carried out as well as microscopic investigations. The accuracies of semi-empirical models to evaluate the kinetics of bacteria growth and to correlate hydraulic properties and microbiological parameters were examined. Permittivity tests under increasing water heads were also performed on the geotextile samples already subjected to long-term leachate flow in order to evaluate the values of water heads required to wash the biofilms out of the geotextile pores. The results of the tests showed the marked reduction of geotextile permeability due to biological clogging and that the results of the predictions by semi-empirical methods were consistent with the biological mechanisms observed.

Research paper thumbnail of Tailings-nonwoven geotextile filter compatibility in mining applications

Geotextiles and Geomembranes, 2010

ABSTRACT Nonwoven geotextiles have been commonly used in filtration and drainage of geotechnical ... more ABSTRACT Nonwoven geotextiles have been commonly used in filtration and drainage of geotechnical engineering works. This paper presents a study on the use of such materials in drainage and filtration systems of tailings dams. Different combinations of tailings and geotextiles were submitted to gradient ratio (GR) tests under confinement in the laboratory with varying values of stress levels and hydraulic gradients. The results of GR tests under confining stresses up to 2000kPa are presented and discussed. The dimensions of the tailings particles entrapped in the geotextile specimens and those that piped through the geotextile were also assessed. Geotextile specimens from the drainage system of a tailings dam were exhumed for analyses, as part of the research programme. The results obtained showed that stress levels and the hydraulic gradients used in the tests influenced the behaviour of the system. Physical and microscopic analyses of the specimens tested showed greater geotextile impregnation by tailings particles in the field than in the laboratory. The overall performance of the geotextiles tested under laboratory conditions was satisfactory. However, in the field segregation of tailings particles and transport of fines in suspension can subject the filter to more complex and severe clogging mechanisms, not properly simulated in current standard testing procedures.

Research paper thumbnail of Sagging and filtration behaviour of nonwoven geotextiles overlying different bedding materials

Geotextiles and Geomembranes, 2012

This paper presents and discusses the results obtained in laboratory tests to evaluate sagging an... more This paper presents and discusses the results obtained in laboratory tests to evaluate sagging and filtration behaviour of nonwoven geotextiles overlying particles of different bedding materials. Nonwoven geotextiles with masses per unit area of 200 g/m 2 , 400 g/m 2 and 600 g/m 2 were used in the tests. Stainless steel spheres and gravels were employed as granular materials underlying the geotextile filter. Specific tests to evaluate the intensity of sagging of the geotextile filter in the voids of the underlying material were carried out. Average strains mobilised in the geotextile were assessed in the tests. The grain sizes of the particles that piped through the geotextile filter for different arrangements of spheres as bedding layer for the filter were measured. The results obtained showed that bedding conditions and geotextile structural characteristics can influence its retention capacity. Good comparisons between predicted and measured average geotextile strains were observed.

Research paper thumbnail of Behaviour of a geogrid reinforced wall built with recycled construction and demolition waste backfill on a collapsible foundation

Geotextiles and Geomembranes, 2013

ABSTRACT

Research paper thumbnail of Microstructure and pore characteristics of synthetic filters under confinement

Research paper thumbnail of Characterisation of permeability to gas of geosynthetic clay liners in unsaturated conditions

Geosynthetics International, 2011

This paper is a contribution to the characterisation of permeability to gas of unsaturated GCLs, ... more This paper is a contribution to the characterisation of permeability to gas of unsaturated GCLs, with applications in cover liners of municipal solid waste landfills. Conducting such tests at low gas pressure gradient limits the risk of moisture distribution change in the bentonite, which has been observed under high pressure gradients. However, a consequence of a low pressure gradient is a small gas flow rate that is difficult to measure with good accuracy. Therefore a solution may be the use of transient state tests, such as the falling pressure test adapted to GCL permeability characterisation. This paper shows the influence of the main parameters related to the test, and to the material tested (natural or activated calcium bentonite, moisture content, presence or not of small cracks in the bentonite). The results obtained showed good repeatability for gas differential pressures up to 40 kPa for the test conditions employed in this work. The results showed that the gravimetric moisture content of the GCL necessary to attain a certain permeability value depends on the nature of the bentonite, which was not observed in terms of volumetric moisture content. However, other factors were shown to be more important than the nature of bentonite in GCL permeability to gas: the desiccation due to the gas flow can significantly increase the permeability, which compromises the GCL's performance as a gas barrier.

Research paper thumbnail of Soil–geotextile filter interaction under high stress levels in the gradient ratio test

Geosynthetics International, 2005

ABSTRACT This paper presents the results of gradient ratio tests on different soil - geotextile s... more ABSTRACT This paper presents the results of gradient ratio tests on different soil - geotextile systems under normal stresses up to 2000 kPa. Different types of soil and geotextiles were tested, and the soil particles that passed through the geotextile and those retained in it were collected for particle size analyses. The results obtained show that the use of definitions of gradient ratio based on the measurement of water heads close to the geotextile layer can be useful for a better identification of geotextile-clogging mechanisms. The entrapment of soil particles in the geotextile increases its retaining capacity and alters the conditions for further clogging. The dimensions of the entrapped soil particles can be greater than the geotextile pore dimensions under unconfined conditions and are controlled by soil and geotextile characteristics and by the soil sample preparation technique employed. The results suggest that current retention and permeability criteria for geotextile filters can be excessively conservative. Discussions on geotextile performance in the test and under field conditions are also presented as well as limitations and new proposals for the interpretation of the gradient ratio test.

Research paper thumbnail of Protection of buried pipes against accidental damage using geosynthetics

Geosynthetics International, 2010

ABSTRACT

Research paper thumbnail of Comparisons between predicted and observed behaviour of a geosynthetic reinforced abutment on soft soil

Engineering Geology, 2012

The use of soil reinforcement for the construction of embankments on soft soils has become an inc... more The use of soil reinforcement for the construction of embankments on soft soils has become an increasing practice. This paper presents comparisons between predicted and observed behaviour of a geogrid reinforced abutment on soft soil using a finite element code. The problem is quite complex in terms of geometry and soil conditions. The results obtained in the numerical simulation were compared to the results obtained from instrumentation. The numerical analysis was able to provide good comparisons between calculated and measured vertical displacements and maximum excess pore pressures using back-calculated consolidation properties. However, significant deviations were observed for horizontal displacements and reinforcement forces. Despite some limitations of the numerical tool employed, the results obtained showed that the design could have been improved had such numerical analysis been carried out.

Research paper thumbnail of A study on the behaviour of soil–geotextile systems in filtration tests

Canadian Geotechnical Journal, 1996

The behaviour of soil–geotextile systems in filtration tests is reported for nonwoven geotextiles... more The behaviour of soil–geotextile systems in filtration tests is reported for nonwoven geotextiles under unidirectional flow. A new apparatus was developed to preform filtration tests under an applied vertical stress, and tests were then conducted with different soils and nonwoven geotextiles in order to evaluate the clogging potential and retention capacity of these materials under rather severe combinations of geotextile and soil characteristics. Results show that the geotextiles perfomed well and that observed permeability losses were acceptable even for gradient ratios close to 3. No progressive piping was observed, and it is believed that the retention capacity of the geotextiles may be influenced by their manufacturing process. In general, theoretical predictions for the maximum particle size passing through the geotextile compared well with measurements. Key words: geotextiles, filtration, gradient ratio, permeability, soil retention, clogging.