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Papers by domenico ielo

Research paper thumbnail of Modelling long-term hydraulic conductivity behaviour of zero valent iron column tests for permeable reactive barrier design

Canadian Geotechnical Journal, 2016

In this paper, a numerical model to simulate the hydraulic conductivity reduction observed during... more In this paper, a numerical model to simulate the hydraulic conductivity reduction observed during long-term laboratory column tests is proposed. The column tests are carried out to study dissolved heavy metals removal by using granular zero valent iron (ZVI). The proposed model is also used to analyse the main causes of hydraulic conductivity reduction observed during laboratory column tests. Expansive iron corrosion, precipitation of reaction products, and gas formation are the processes considered in the proposed model. Numerical simulation results show that to reproduce hydraulic behaviour of the experimental systems, the change of pores geometry due to expansive iron corrosion and precipitation of reaction products, which determines a possible stoppage of gas bubbles, should be considered. Furthermore, model results show that only a small percentage of the iron available is corroded during the tests (from 0.4% to 1.9%). According to the model, the average diameter of gas bubbles...

Research paper thumbnail of Predicting the Saturated Hydraulic Conductivity of Clayey Soils and Clayey or Silty Sands

Predictive models able to provide a reliable estimate of hydraulic conductivity can be useful in ... more Predictive models able to provide a reliable estimate of hydraulic conductivity can be useful in various geotechnical applications. Since most of the existing predictive methods for saturated hydraulic conductivity estimation are valid only for a limited range of soils or can be applied under certain restrictive conditions, a new method applicable to clayey soils and clayey or silty sands having a wide range of values of soil index properties is proposed in this study. For this purpose, 329 saturated hydraulic conductivity values, obtained by laboratory tests carried out on different soils, were collected in a database and used to develop five equations using a multiple regression approach. Each equation correlates the hydraulic conductivity with one or more geotechnical parameters. An equation was developed that predicts, within an order of magnitude, the saturated hydraulic conductivity in the range from 1.2 × 10−11 to 3.9 × 10−6 m/s, based on simple geotechnical parameters (i.e.,...

Research paper thumbnail of Recent developments in the design of geotextile filters

Research paper thumbnail of Reply to the discussion by Dallo and Wang on "A new theoretical method to evaluate the internal stability of granular soils" 1

Research paper thumbnail of Recenti sviluppi nella progettazione dei geotessili con funzione di filtro

Research paper thumbnail of Valutazione della stabilità interna dei terreni granulari

Research paper thumbnail of Reactive and Hydraulic Behavior of Permeable Reactive Barriers Constituted by Fe0 and Granular Mixtures of Fe0/Pumice

Procedia Engineering, 2016

Abstract The objective of the present work is to analyze, by means of column tests, the reactivit... more Abstract The objective of the present work is to analyze, by means of column tests, the reactivity and hydraulic long term behavior of the zero valent iron (Fe 0 ) and of a granular mixture Fe 0 /pumice, for the remediation, through the Permeable Reactive Barriers technology, of nickel contaminated groundwater. The reactive behavior was studied by analyzing nickel concentration data, through a first order kinetic model in order to determine the thickness of a hypothetical PRB and its variation over time. The hydraulic conductivity behavior was studied through a numerical-statistical geometrical model developed by the authors. Expansive iron corrosion, precipitation of reaction products and gas formation are the processes considered.

Research paper thumbnail of Reply to the discussion by Dallo and Wang on “A new theoretical method to evaluate the internal stability of granular soils”1 1 Appears in the Canadian Geotechnical Journal, 49(7): 866–868

Canadian Geotechnical Journal

Research paper thumbnail of Reply to the discussion by Ni et al. on “Analysis of the internal stability of granular soils using different methods” 1

Canadian Geotechnical Journal, 2015

Research paper thumbnail of A new theoretical method to evaluate the upper limit of the retention ratio for the design of geotextile filters in contact with broadly granular soils

Geotextiles and Geomembranes, 2012

Research paper thumbnail of Analysis of the internal stability of granular soils using different methods

Canadian Geotechnical Journal, 2014

ABSTRACT The knowledge of the internal stability of granular soils is a key factor in the design ... more ABSTRACT The knowledge of the internal stability of granular soils is a key factor in the design of granular or geotextile filters. In order to evaluate the internal stability of granular soils different semi-empirical methods are generally used. Nevertheless, the results of these methods, on the same soil, can lead to different internal stability evaluations. In this paper, in order to evaluate the reliability of the semi-empirical methods available in literature, the internal stability of different granular soils, reconstituted by the authors and by other researchers, has been studied by means of theoretical and experimental approaches. In particular, the theoretical analysis of the internal stability was performed using the Simulfiltr method, developed recently by the authors, while the experimental evaluation of the internal stability was carried out by means of long term filtration tests using a new test procedure. The comparison of the internal stability analysis performed by means of semi-empirical, theoretical and experimental methods showed that the semi-empirical methods are not always reliable. Therefore, on the base of these results, a new chart, in terms of minimum slope Smin (%) of the grain size distribution and of average value of finer percentage F, has been proposed in order to evaluate the internal stability of granular soils.

Research paper thumbnail of A new theoretical method to evaluate the internal stability of granular soils

Canadian Geotechnical Journal, 2012

ABSTRACT The geotextile filter design is particularly complex when granular base soils are intern... more ABSTRACT The geotextile filter design is particularly complex when granular base soils are internally unstable. In these conditions,the design criteria available in literature are not always reliable. This paper deals with a new theoretical method developed to evaluate the internal stability of granular soils. To simulate, theoretically, the filtration process inside these soils, a set of spherical particles and different soil relative densities have been considered. The soil has been represented by means of a sequence of parallel layers, containing constrictions and particles, placed upon each other at a distance, in the direction of hydraulic flow, which is a function of the soil relative density. The movement of the fine particles through the different soil layers has been simulated by means of a mechanism that compares each particle contained in the i layer with the constrictions contained in the next i + 1 layer. The results of the numerical simulations were used to evaluate the internal stability of the analyzed granular soil and the corresponding critical diameter of suffusion, Dc. Finally, the reliability of the proposed theoretical method was evaluated by means of the results of experimental long-term filtration tests performed using a rigid-wall permeameter on different unstable granular soils.

Research paper thumbnail of Corrigendum: A new theoretical method to evaluate the internal stability of granular soils

Canadian Geotechnical Journal, 2012

Research paper thumbnail of Recent developments in the design of geotextile filters

Since decades the use of geotextile filters is a common application in geotechnical and geo-envir... more Since decades the use of geotextile filters is a common application in geotechnical and geo-environmental engineering. As well known, the geotextile filter design is based on the retention and the permeability criteria. Generally, the retention criterion that a geotextile filter must satisfy in comparison to the base soil is expressed in terms of geotextile characteristic opening size and of an indicative soil particle diameter. The criterion works if the larger particles retain the smaller particles and this condition is verified when these particles form the solid skeleton. In some granular soils, internally unstable or with a broadly grain size distribution if the retention criterion is satisfied, this condition does not guarantee that the whole base soil is retained. In fact, the base soil could be subjected to an internal erosion phenomenon if the geotextile filter characteristic opening size is too large and if the larger particles retained by the filter are not able to retain the smaller particles of the base soil and a hydraulic flow of dragging exists. In these conditions, the knowledge of the internal stability of granular soils is a key-factor in the design of geotextile filters. Therefore, in order to evaluate the internal stability of granular soils, different methods are generally available and the results of the application of these methods, on the same soil, can lead to different internal stability evaluations. In this invited lecture, the most recent methods to evaluate the internal stability of granular soils are analysed. Moreover, a method that allows determining the upper limit value of the geotextile filter characteristic opening size to be used in the retention criterion in order to avoid the internal erosion of broadly granular base soils is shown.

Research paper thumbnail of Modelling long-term hydraulic conductivity behaviour of zero valent iron column tests for permeable reactive barrier design

Canadian Geotechnical Journal, 2016

In this paper, a numerical model to simulate the hydraulic conductivity reduction observed during... more In this paper, a numerical model to simulate the hydraulic conductivity reduction observed during long-term laboratory column tests is proposed. The column tests are carried out to study dissolved heavy metals removal by using granular zero valent iron (ZVI). The proposed model is also used to analyse the main causes of hydraulic conductivity reduction observed during laboratory column tests. Expansive iron corrosion, precipitation of reaction products, and gas formation are the processes considered in the proposed model. Numerical simulation results show that to reproduce hydraulic behaviour of the experimental systems, the change of pores geometry due to expansive iron corrosion and precipitation of reaction products, which determines a possible stoppage of gas bubbles, should be considered. Furthermore, model results show that only a small percentage of the iron available is corroded during the tests (from 0.4% to 1.9%). According to the model, the average diameter of gas bubbles...

Research paper thumbnail of Predicting the Saturated Hydraulic Conductivity of Clayey Soils and Clayey or Silty Sands

Predictive models able to provide a reliable estimate of hydraulic conductivity can be useful in ... more Predictive models able to provide a reliable estimate of hydraulic conductivity can be useful in various geotechnical applications. Since most of the existing predictive methods for saturated hydraulic conductivity estimation are valid only for a limited range of soils or can be applied under certain restrictive conditions, a new method applicable to clayey soils and clayey or silty sands having a wide range of values of soil index properties is proposed in this study. For this purpose, 329 saturated hydraulic conductivity values, obtained by laboratory tests carried out on different soils, were collected in a database and used to develop five equations using a multiple regression approach. Each equation correlates the hydraulic conductivity with one or more geotechnical parameters. An equation was developed that predicts, within an order of magnitude, the saturated hydraulic conductivity in the range from 1.2 × 10−11 to 3.9 × 10−6 m/s, based on simple geotechnical parameters (i.e.,...

Research paper thumbnail of Recent developments in the design of geotextile filters

Research paper thumbnail of Reply to the discussion by Dallo and Wang on "A new theoretical method to evaluate the internal stability of granular soils" 1

Research paper thumbnail of Recenti sviluppi nella progettazione dei geotessili con funzione di filtro

Research paper thumbnail of Valutazione della stabilità interna dei terreni granulari

Research paper thumbnail of Reactive and Hydraulic Behavior of Permeable Reactive Barriers Constituted by Fe0 and Granular Mixtures of Fe0/Pumice

Procedia Engineering, 2016

Abstract The objective of the present work is to analyze, by means of column tests, the reactivit... more Abstract The objective of the present work is to analyze, by means of column tests, the reactivity and hydraulic long term behavior of the zero valent iron (Fe 0 ) and of a granular mixture Fe 0 /pumice, for the remediation, through the Permeable Reactive Barriers technology, of nickel contaminated groundwater. The reactive behavior was studied by analyzing nickel concentration data, through a first order kinetic model in order to determine the thickness of a hypothetical PRB and its variation over time. The hydraulic conductivity behavior was studied through a numerical-statistical geometrical model developed by the authors. Expansive iron corrosion, precipitation of reaction products and gas formation are the processes considered.

Research paper thumbnail of Reply to the discussion by Dallo and Wang on “A new theoretical method to evaluate the internal stability of granular soils”1 1 Appears in the Canadian Geotechnical Journal, 49(7): 866–868

Canadian Geotechnical Journal

Research paper thumbnail of Reply to the discussion by Ni et al. on “Analysis of the internal stability of granular soils using different methods” 1

Canadian Geotechnical Journal, 2015

Research paper thumbnail of A new theoretical method to evaluate the upper limit of the retention ratio for the design of geotextile filters in contact with broadly granular soils

Geotextiles and Geomembranes, 2012

Research paper thumbnail of Analysis of the internal stability of granular soils using different methods

Canadian Geotechnical Journal, 2014

ABSTRACT The knowledge of the internal stability of granular soils is a key factor in the design ... more ABSTRACT The knowledge of the internal stability of granular soils is a key factor in the design of granular or geotextile filters. In order to evaluate the internal stability of granular soils different semi-empirical methods are generally used. Nevertheless, the results of these methods, on the same soil, can lead to different internal stability evaluations. In this paper, in order to evaluate the reliability of the semi-empirical methods available in literature, the internal stability of different granular soils, reconstituted by the authors and by other researchers, has been studied by means of theoretical and experimental approaches. In particular, the theoretical analysis of the internal stability was performed using the Simulfiltr method, developed recently by the authors, while the experimental evaluation of the internal stability was carried out by means of long term filtration tests using a new test procedure. The comparison of the internal stability analysis performed by means of semi-empirical, theoretical and experimental methods showed that the semi-empirical methods are not always reliable. Therefore, on the base of these results, a new chart, in terms of minimum slope Smin (%) of the grain size distribution and of average value of finer percentage F, has been proposed in order to evaluate the internal stability of granular soils.

Research paper thumbnail of A new theoretical method to evaluate the internal stability of granular soils

Canadian Geotechnical Journal, 2012

ABSTRACT The geotextile filter design is particularly complex when granular base soils are intern... more ABSTRACT The geotextile filter design is particularly complex when granular base soils are internally unstable. In these conditions,the design criteria available in literature are not always reliable. This paper deals with a new theoretical method developed to evaluate the internal stability of granular soils. To simulate, theoretically, the filtration process inside these soils, a set of spherical particles and different soil relative densities have been considered. The soil has been represented by means of a sequence of parallel layers, containing constrictions and particles, placed upon each other at a distance, in the direction of hydraulic flow, which is a function of the soil relative density. The movement of the fine particles through the different soil layers has been simulated by means of a mechanism that compares each particle contained in the i layer with the constrictions contained in the next i + 1 layer. The results of the numerical simulations were used to evaluate the internal stability of the analyzed granular soil and the corresponding critical diameter of suffusion, Dc. Finally, the reliability of the proposed theoretical method was evaluated by means of the results of experimental long-term filtration tests performed using a rigid-wall permeameter on different unstable granular soils.

Research paper thumbnail of Corrigendum: A new theoretical method to evaluate the internal stability of granular soils

Canadian Geotechnical Journal, 2012

Research paper thumbnail of Recent developments in the design of geotextile filters

Since decades the use of geotextile filters is a common application in geotechnical and geo-envir... more Since decades the use of geotextile filters is a common application in geotechnical and geo-environmental engineering. As well known, the geotextile filter design is based on the retention and the permeability criteria. Generally, the retention criterion that a geotextile filter must satisfy in comparison to the base soil is expressed in terms of geotextile characteristic opening size and of an indicative soil particle diameter. The criterion works if the larger particles retain the smaller particles and this condition is verified when these particles form the solid skeleton. In some granular soils, internally unstable or with a broadly grain size distribution if the retention criterion is satisfied, this condition does not guarantee that the whole base soil is retained. In fact, the base soil could be subjected to an internal erosion phenomenon if the geotextile filter characteristic opening size is too large and if the larger particles retained by the filter are not able to retain the smaller particles of the base soil and a hydraulic flow of dragging exists. In these conditions, the knowledge of the internal stability of granular soils is a key-factor in the design of geotextile filters. Therefore, in order to evaluate the internal stability of granular soils, different methods are generally available and the results of the application of these methods, on the same soil, can lead to different internal stability evaluations. In this invited lecture, the most recent methods to evaluate the internal stability of granular soils are analysed. Moreover, a method that allows determining the upper limit value of the geotextile filter characteristic opening size to be used in the retention criterion in order to avoid the internal erosion of broadly granular base soils is shown.