Ghada Ellithy | West Virginia University (original) (raw)

Papers by Ghada Ellithy

Research paper thumbnail of Erosion rate equations for coarse- grained materials using a small flume testing

Scour and Erosion IX, 2018

Erosion rate of soils during a levee or dam overtopping event is a major component in risk assess... more Erosion rate of soils during a levee or dam overtopping event is a major component in risk assessment evaluation of breach time and consequently in determining the downstream consequences. There is uncertainty in estimation of the erosion rate especially for coarsegrained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, erosion rate results are presented on three soil mixes that share the same median grain size D50 of 2 mm, the fines content varies between zero and 20%, and the gravel content between zero and 30%. Each of the three mixes is compacted in the box at optimum or near optimum moisture content as determined from standard Proctor test. The box measures 0.3 m wide x 0.6 m long x 0.15 m deep. Each material is tested several times at varying hydraulic loading to determine the erosion rate after equal time intervals. The water depth, velocity are measured at each hydraulic loading and the acting bed shear is calculated. The validity of the excess shear stress equation is discussed as well as other bilinear and nonlinear models that could fit the erosion rate of such materials as it relates to the acting bed shear stress. The effect of fines content and level of acting shear stresses are presented in the paper.

Research paper thumbnail of Using Machine Learning in Estimating Changing Bed Shear over a Flume Test Box

Research paper thumbnail of Effect of Suction and Confining Pressure on Shear Strength and Dilatancy of Highly Compacted Silty Sand: Single-Stage versus Multistage Triaxial Testing

Geotechnical Testing Journal, 2020

Evaluating short- and long-term performance of engineered earthen structures and slopes requires ... more Evaluating short- and long-term performance of engineered earthen structures and slopes requires proper understanding of the behavior of compacted and highly compacted soils. However, limited studies exist in the literature of unsaturated soil mechanics experimentally testing highly compacted soils, which often possess complex shear strength and dilatancy characteristics. The main objective of this study is to investigate the effect of suction and confining pressure on shear strength and dilatancy of a highly compacted silty sand through multistage and single-stage triaxial testing. Multistage triaxial testing offers a time and cost efficient approach that can reasonably represent field conditions where soils experience fluctuations in external loading conditions (e.g., flood loading/unloading). This article presents the results of consolidated drained multistage and single-stage triaxial tests on highly compacted silty sand under saturated and unsaturated conditions. Soil specimens were isotropically consolidated at a constant matric suction of 0 (saturated), 20, 50, and 95 kPa under net confining pressures of 50, 100, and 200 kPa. Unsaturated specimens consistently exhibited higher shear strength in multistage and single-stage tests compared to saturated specimens. Peak state lines for all unsaturated tests were plotted and found to be near parallel to the saturated peak state line. All tested specimens exhibited dilatancy following a small initial contraction. Although the dilatancy during shearing in multistage tests was comparable to that in the single-stage tests, the cumulative volumetric strain resulted in a net increase in the specimen volume in the case of unsaturated tests, and a net decrease in the case of saturated tests. This difference in volumetric strain behavior resulted in a lower peak shear strength of the saturated specimens tested using multistage testing compared to single stage but a higher peak shear strength in the case of the unsaturated specimens.

Research paper thumbnail of Case Study: Unsaturated Embankment Failure on Soft Soils

Journal of Geotechnical and Geoenvironmental Engineering, 2020

Research paper thumbnail of Integrating Field Monitoring and Numerical Modeling to Evaluate Performance of a Levee under Climatic and Tidal Variations

Journal of Geotechnical and Geoenvironmental Engineering, 2019

Research paper thumbnail of Spreadsheet for estimating soil water characteristic curves (SWCC)

PURPOSE: SWCC can be measured in the lab; however, due to the cost, time, and high variability in... more PURPOSE: SWCC can be measured in the lab; however, due to the cost, time, and high variability in the results, empirical equations were developed using multiple regression approaches on databases consisting of a large number of measured SWCCs. The spreadsheet presented herein utilizes different methods that use basic soil properties, such as grain size distribution and Atterberg limits, to calculate the input parameters for van Genuchten and Fredlund and Xing equations. These parameters are required by numerical models, such as SEEP/W, to perform transient seepage analysis. The spreadsheet allows copying the generated curve data points as well as an input into the numerical model. The spreadsheet calculates the SWCCs using seven different methods for comparison. It also compares four closed form models, Gardner (1958), Brooks and Corey (1964), van Genuchten (1980), and Fredlund and Xing (1994), given the model parameters are known. INTRODUCTION: A steady-state condition for a given seepage scenario indicates that input and output quantities, such as soil hydraulic loading, gradient, and flow rate, remain unchanged with time. When the hydraulic properties of the flow medium and the flow characteristics change with time due to changing of hydraulic boundary conditions, river water level for example, it is referred to as transient flow. Steady-state flow can occur in partially saturated soils, for example, the flow above phreatic surface with constant boundary conditions, as shown in Figure 1. Figure 1. Cross section of unconfined steady-state seepage from EM 1110-2-1901. Unsaturated flow often refers to flow through soils with negative pore pressures. This can occur in unsaturated soils, where the pores are partially filled with water; however, soil can remain saturated for some distance above the phreatic surface under negative pore pressures. Flow above the phreatic surface through the saturated zone is also considered unsaturated flow. The assumption that the flow has achieved a steady-state condition is usually conservative from an engineering perspective. Steady-state analyses will normally result in the highest vertical gradients, uplift pressures, flows, and pore pressures that the structures should experience.

Research paper thumbnail of Evaluation of Erosion Rate of Coarse-Grained Materials Using a New Lidar Technology

Research paper thumbnail of Determination of erosion parameters of coarse-grained materials using a small flume

Overtopping is one of the major causes of dams and levees failure. There is uncertainty in estima... more Overtopping is one of the major causes of dams and levees failure. There is uncertainty in estimation of the erosion parameters especially for coarse- grained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, results from a box test performed on three coarse grained materials in a 0.3-meter wide flume are discussed. The three materials share the same median grain size D50 of 2 mm, however, they vary in fines content between zero to 20%. The box measured 0.3 m wide x 0.6 m long x 0.15 m deep. Each of the three materials was compacted in the box at near optimum moisture content and dry density as determined from standard Proctor test. Each material was tested at varying hydraulic loadings to determine the erosion rate after equal time intervals. The water depth and velocity were measured at each hydraulic loading using Pitot tubes and the acting bed shear was calculated. The effect of fines content...

Research paper thumbnail of Monte Carlo Simulations of Coupled Transient Seepage Flow and Compressive Stress in Levees

Abstract. The purpose of this research is to compare the results from two different computer prog... more Abstract. The purpose of this research is to compare the results from two different computer programs of flow analyses of two levees at Port Arthur, Texas where rising water of a flood from Hurricane Ike occurred on the levees. The first program (Program 1) is a two-dimensional (2-D) transient finite element program that couples the conservation of mass flow equation with accompanying hydraulic boundary conditions with the conservation of force equations with accompanying x and y displacement and force boundary conditions, thus yielding total head, x displacement, and y displacement as unknowns at each finite element node. The second program (Program 2) is a 2-D transient finite element program that considers only the conservation of mass flow equation with its accompanying hydraulic boundary conditions, yielding only total head as the unknown at each finite element node. Compressive stresses can be computed at the centroid of each finite element when using the coupled program. Prog...

Research paper thumbnail of Monitoring Suction Stress and Effective Stress in a Silty Sand Levee under Seasonal and Tidal Changes

PanAm Unsaturated Soils 2017

Research paper thumbnail of Vertical Load Test on a Drilled Shaft Installed in Glacially Derived Sediments

There are several methods for estimating the axial capacity of drilled shafts installed in coarse... more There are several methods for estimating the axial capacity of drilled shafts installed in coarse-grained soils. Most methods estimate the ultimate capacity for side friction and tip resistance. Design capacity is then calculated by applying a resistance factor to the ultimate capacity. In reality, however, ultimate resistance may not be mobilized except after a significant displacement that is not structurally tolerated in either compression or tension modes. A fullscale load test is the best way to obtain the load settlement curve for a drilled shaft, especially in soil formations where accurate estimation of soil frictional properties from a field investigation may be difficult. This paper presents the results of a static, axial, compressive bi-directional load test, using the Osterberg method (O-cell test). The test was designed so that the shaft above the O-cell would move up and the shaft below it would move down when loaded. At the start of the test the concrete around the O-...

Research paper thumbnail of Accuracy Assessment of Predictive SWCC Models for Estimating the van Genuchten Model Parameters

Research paper thumbnail of Monte Carlo Simulations of Coupled Transient Seepage Flow and Soil Deformation in Levees

Scalable Computing: Practice and Experience

The purpose of this research is to compare the results from two different computer programs of fl... more The purpose of this research is to compare the results from two different computer programs of flow analysesof two levees at Port Arthur, Texas where rising water of a flood from Hurricane Ike occurred on the levees. The first program (Program 1) is a two-dimensional (2-D) transient finite element program that couples the conservation of mass flow equation with accompanying hydraulic boundary conditions with the conservation of force equations with accompanying x and y displacement and force boundary conditions, thus yielding total head, x displacement, and y displacement as unknowns at each finite element node. The second program (Program 2) is a 2-D transient finite element program that considers only the conservation of mass flowequation with its accompanying hydraulic boundary conditions, yielding only total head as the unknown at each finite element node. Compressive stresses can be computed at the centroid of each finite element when using the coupled program. Programs 1 and 2...

Research paper thumbnail of Effects of Climate Change on Fragility Curves of Earthen Levees Subjected to Extreme Precipitations

Research paper thumbnail of Evaluating the mechanisms of erosion for coarse-grained materials

E3S Web of Conferences, 2016

Efforts are currently underway by the U.S. Army Corps of Engineers (USACE) to perform a risk asse... more Efforts are currently underway by the U.S. Army Corps of Engineers (USACE) to perform a risk assessment of all dams and levees within their portfolio. The vast majority of that portfolio is earthen structures. Findings from the assessments have shown that the major risk drivers for these earth structures are related to erosion (internal and external), overtopping, poorly designed and constructed intrusions (such as pipe crossings), and other factors to a lesser degree (such as burrowing animals). Therefore, the USACE is currently investigating several of these failure modes with emphasis on internal and external erosion. This paper will highlight efforts to investigate surface erosion, which may lead to breach formation and growth, by use of laboratory scale model testing to understand and properly capture the physics of the problem. These data are informing improvement and development of numeral methods for use in ongoing risk assessments.

Research paper thumbnail of On-line interactive landfill design calculators assist in proper design and regu- latory compliance

ABSTRACT Landfill designers rely upon a variety of calculations during the design process in orde... more ABSTRACT Landfill designers rely upon a variety of calculations during the design process in order to demonstrate regulatory compliance and ensure proper design. Cre- ating a simplified yet accurate means of completing these calculations is the goal of www.landfilldesign.com. Among the calculators available are USEPA HELP Model analyses, landfill surface water drainage, landfill gas venting design, landfill slope stability, and others. Many of these calculators demonstrate the vital role that geosynthetic materials play in landfill design, from both cost and function perspectives. Geosynthetic-based designs are also available for such applications as Geotextile Filter Design, Leakage through Composite Barriers, Geomembrane Anchorage, and others. Selective design topics are presented here with descriptions of associated Web-based interactive design calculators. All of the design calculators are based on state-of-the-practice principles, in an open-box format (i.e., design equations are given and rel- evant references provided). This format gives the user and reviewer confidence in the accuracy and ap- propriateness of each calculator. The authors welcome readers to use the "Discussion Board" on the Web site for any questions, comments or suggestions for other calculators. Landfill lateral drainage system calculators Lateral drainage systems within modern landfills must perform one or more of the following functions:

Research paper thumbnail of Erosion rate equations for coarse- grained materials using a small flume testing

Scour and Erosion IX, 2018

Erosion rate of soils during a levee or dam overtopping event is a major component in risk assess... more Erosion rate of soils during a levee or dam overtopping event is a major component in risk assessment evaluation of breach time and consequently in determining the downstream consequences. There is uncertainty in estimation of the erosion rate especially for coarsegrained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, erosion rate results are presented on three soil mixes that share the same median grain size D50 of 2 mm, the fines content varies between zero and 20%, and the gravel content between zero and 30%. Each of the three mixes is compacted in the box at optimum or near optimum moisture content as determined from standard Proctor test. The box measures 0.3 m wide x 0.6 m long x 0.15 m deep. Each material is tested several times at varying hydraulic loading to determine the erosion rate after equal time intervals. The water depth, velocity are measured at each hydraulic loading and the acting bed shear is calculated. The validity of the excess shear stress equation is discussed as well as other bilinear and nonlinear models that could fit the erosion rate of such materials as it relates to the acting bed shear stress. The effect of fines content and level of acting shear stresses are presented in the paper.

Research paper thumbnail of Using Machine Learning in Estimating Changing Bed Shear over a Flume Test Box

Research paper thumbnail of Effect of Suction and Confining Pressure on Shear Strength and Dilatancy of Highly Compacted Silty Sand: Single-Stage versus Multistage Triaxial Testing

Geotechnical Testing Journal, 2020

Evaluating short- and long-term performance of engineered earthen structures and slopes requires ... more Evaluating short- and long-term performance of engineered earthen structures and slopes requires proper understanding of the behavior of compacted and highly compacted soils. However, limited studies exist in the literature of unsaturated soil mechanics experimentally testing highly compacted soils, which often possess complex shear strength and dilatancy characteristics. The main objective of this study is to investigate the effect of suction and confining pressure on shear strength and dilatancy of a highly compacted silty sand through multistage and single-stage triaxial testing. Multistage triaxial testing offers a time and cost efficient approach that can reasonably represent field conditions where soils experience fluctuations in external loading conditions (e.g., flood loading/unloading). This article presents the results of consolidated drained multistage and single-stage triaxial tests on highly compacted silty sand under saturated and unsaturated conditions. Soil specimens were isotropically consolidated at a constant matric suction of 0 (saturated), 20, 50, and 95 kPa under net confining pressures of 50, 100, and 200 kPa. Unsaturated specimens consistently exhibited higher shear strength in multistage and single-stage tests compared to saturated specimens. Peak state lines for all unsaturated tests were plotted and found to be near parallel to the saturated peak state line. All tested specimens exhibited dilatancy following a small initial contraction. Although the dilatancy during shearing in multistage tests was comparable to that in the single-stage tests, the cumulative volumetric strain resulted in a net increase in the specimen volume in the case of unsaturated tests, and a net decrease in the case of saturated tests. This difference in volumetric strain behavior resulted in a lower peak shear strength of the saturated specimens tested using multistage testing compared to single stage but a higher peak shear strength in the case of the unsaturated specimens.

Research paper thumbnail of Case Study: Unsaturated Embankment Failure on Soft Soils

Journal of Geotechnical and Geoenvironmental Engineering, 2020

Research paper thumbnail of Integrating Field Monitoring and Numerical Modeling to Evaluate Performance of a Levee under Climatic and Tidal Variations

Journal of Geotechnical and Geoenvironmental Engineering, 2019

Research paper thumbnail of Spreadsheet for estimating soil water characteristic curves (SWCC)

PURPOSE: SWCC can be measured in the lab; however, due to the cost, time, and high variability in... more PURPOSE: SWCC can be measured in the lab; however, due to the cost, time, and high variability in the results, empirical equations were developed using multiple regression approaches on databases consisting of a large number of measured SWCCs. The spreadsheet presented herein utilizes different methods that use basic soil properties, such as grain size distribution and Atterberg limits, to calculate the input parameters for van Genuchten and Fredlund and Xing equations. These parameters are required by numerical models, such as SEEP/W, to perform transient seepage analysis. The spreadsheet allows copying the generated curve data points as well as an input into the numerical model. The spreadsheet calculates the SWCCs using seven different methods for comparison. It also compares four closed form models, Gardner (1958), Brooks and Corey (1964), van Genuchten (1980), and Fredlund and Xing (1994), given the model parameters are known. INTRODUCTION: A steady-state condition for a given seepage scenario indicates that input and output quantities, such as soil hydraulic loading, gradient, and flow rate, remain unchanged with time. When the hydraulic properties of the flow medium and the flow characteristics change with time due to changing of hydraulic boundary conditions, river water level for example, it is referred to as transient flow. Steady-state flow can occur in partially saturated soils, for example, the flow above phreatic surface with constant boundary conditions, as shown in Figure 1. Figure 1. Cross section of unconfined steady-state seepage from EM 1110-2-1901. Unsaturated flow often refers to flow through soils with negative pore pressures. This can occur in unsaturated soils, where the pores are partially filled with water; however, soil can remain saturated for some distance above the phreatic surface under negative pore pressures. Flow above the phreatic surface through the saturated zone is also considered unsaturated flow. The assumption that the flow has achieved a steady-state condition is usually conservative from an engineering perspective. Steady-state analyses will normally result in the highest vertical gradients, uplift pressures, flows, and pore pressures that the structures should experience.

Research paper thumbnail of Evaluation of Erosion Rate of Coarse-Grained Materials Using a New Lidar Technology

Research paper thumbnail of Determination of erosion parameters of coarse-grained materials using a small flume

Overtopping is one of the major causes of dams and levees failure. There is uncertainty in estima... more Overtopping is one of the major causes of dams and levees failure. There is uncertainty in estimation of the erosion parameters especially for coarse- grained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, results from a box test performed on three coarse grained materials in a 0.3-meter wide flume are discussed. The three materials share the same median grain size D50 of 2 mm, however, they vary in fines content between zero to 20%. The box measured 0.3 m wide x 0.6 m long x 0.15 m deep. Each of the three materials was compacted in the box at near optimum moisture content and dry density as determined from standard Proctor test. Each material was tested at varying hydraulic loadings to determine the erosion rate after equal time intervals. The water depth and velocity were measured at each hydraulic loading using Pitot tubes and the acting bed shear was calculated. The effect of fines content...

Research paper thumbnail of Monte Carlo Simulations of Coupled Transient Seepage Flow and Compressive Stress in Levees

Abstract. The purpose of this research is to compare the results from two different computer prog... more Abstract. The purpose of this research is to compare the results from two different computer programs of flow analyses of two levees at Port Arthur, Texas where rising water of a flood from Hurricane Ike occurred on the levees. The first program (Program 1) is a two-dimensional (2-D) transient finite element program that couples the conservation of mass flow equation with accompanying hydraulic boundary conditions with the conservation of force equations with accompanying x and y displacement and force boundary conditions, thus yielding total head, x displacement, and y displacement as unknowns at each finite element node. The second program (Program 2) is a 2-D transient finite element program that considers only the conservation of mass flow equation with its accompanying hydraulic boundary conditions, yielding only total head as the unknown at each finite element node. Compressive stresses can be computed at the centroid of each finite element when using the coupled program. Prog...

Research paper thumbnail of Monitoring Suction Stress and Effective Stress in a Silty Sand Levee under Seasonal and Tidal Changes

PanAm Unsaturated Soils 2017

Research paper thumbnail of Vertical Load Test on a Drilled Shaft Installed in Glacially Derived Sediments

There are several methods for estimating the axial capacity of drilled shafts installed in coarse... more There are several methods for estimating the axial capacity of drilled shafts installed in coarse-grained soils. Most methods estimate the ultimate capacity for side friction and tip resistance. Design capacity is then calculated by applying a resistance factor to the ultimate capacity. In reality, however, ultimate resistance may not be mobilized except after a significant displacement that is not structurally tolerated in either compression or tension modes. A fullscale load test is the best way to obtain the load settlement curve for a drilled shaft, especially in soil formations where accurate estimation of soil frictional properties from a field investigation may be difficult. This paper presents the results of a static, axial, compressive bi-directional load test, using the Osterberg method (O-cell test). The test was designed so that the shaft above the O-cell would move up and the shaft below it would move down when loaded. At the start of the test the concrete around the O-...

Research paper thumbnail of Accuracy Assessment of Predictive SWCC Models for Estimating the van Genuchten Model Parameters

Research paper thumbnail of Monte Carlo Simulations of Coupled Transient Seepage Flow and Soil Deformation in Levees

Scalable Computing: Practice and Experience

The purpose of this research is to compare the results from two different computer programs of fl... more The purpose of this research is to compare the results from two different computer programs of flow analysesof two levees at Port Arthur, Texas where rising water of a flood from Hurricane Ike occurred on the levees. The first program (Program 1) is a two-dimensional (2-D) transient finite element program that couples the conservation of mass flow equation with accompanying hydraulic boundary conditions with the conservation of force equations with accompanying x and y displacement and force boundary conditions, thus yielding total head, x displacement, and y displacement as unknowns at each finite element node. The second program (Program 2) is a 2-D transient finite element program that considers only the conservation of mass flowequation with its accompanying hydraulic boundary conditions, yielding only total head as the unknown at each finite element node. Compressive stresses can be computed at the centroid of each finite element when using the coupled program. Programs 1 and 2...

Research paper thumbnail of Effects of Climate Change on Fragility Curves of Earthen Levees Subjected to Extreme Precipitations

Research paper thumbnail of Evaluating the mechanisms of erosion for coarse-grained materials

E3S Web of Conferences, 2016

Efforts are currently underway by the U.S. Army Corps of Engineers (USACE) to perform a risk asse... more Efforts are currently underway by the U.S. Army Corps of Engineers (USACE) to perform a risk assessment of all dams and levees within their portfolio. The vast majority of that portfolio is earthen structures. Findings from the assessments have shown that the major risk drivers for these earth structures are related to erosion (internal and external), overtopping, poorly designed and constructed intrusions (such as pipe crossings), and other factors to a lesser degree (such as burrowing animals). Therefore, the USACE is currently investigating several of these failure modes with emphasis on internal and external erosion. This paper will highlight efforts to investigate surface erosion, which may lead to breach formation and growth, by use of laboratory scale model testing to understand and properly capture the physics of the problem. These data are informing improvement and development of numeral methods for use in ongoing risk assessments.

Research paper thumbnail of On-line interactive landfill design calculators assist in proper design and regu- latory compliance

ABSTRACT Landfill designers rely upon a variety of calculations during the design process in orde... more ABSTRACT Landfill designers rely upon a variety of calculations during the design process in order to demonstrate regulatory compliance and ensure proper design. Cre- ating a simplified yet accurate means of completing these calculations is the goal of www.landfilldesign.com. Among the calculators available are USEPA HELP Model analyses, landfill surface water drainage, landfill gas venting design, landfill slope stability, and others. Many of these calculators demonstrate the vital role that geosynthetic materials play in landfill design, from both cost and function perspectives. Geosynthetic-based designs are also available for such applications as Geotextile Filter Design, Leakage through Composite Barriers, Geomembrane Anchorage, and others. Selective design topics are presented here with descriptions of associated Web-based interactive design calculators. All of the design calculators are based on state-of-the-practice principles, in an open-box format (i.e., design equations are given and rel- evant references provided). This format gives the user and reviewer confidence in the accuracy and ap- propriateness of each calculator. The authors welcome readers to use the "Discussion Board" on the Web site for any questions, comments or suggestions for other calculators. Landfill lateral drainage system calculators Lateral drainage systems within modern landfills must perform one or more of the following functions: