CURRENT GRADUATE STUDENTS

Ph.D. CANDIDATES

M.Sc. STUDENTS

Abdel-Atty, Khaled
 
An Experimental and Theoretical Evaluation of the Environmental Protection Provided by the Composite Liner Systems
An Experimental program has been developed to investigate the environmental protection provided by composite liner systems. The research program has both and experimental and theoretical component.  The eexperimental program will quantify contaminant migration through a GM with a hole of a known size resting on either a GCL and sand foundation.  These tests are designed to simulate the scenario where a hole develops in the GM several years after installation from a gravel puncture or stress cracking.  Migration of NaCl  will be monitored both directly beneath the GCL and at various locations in the sand layer or compacted clay using conductivity sensors.  The effect of the interface contact between the GM and underlying material on contaminant transport will be quantified.  Finite-layer and 3D finite-element numerical techniques will be used to interpret the results from the experiments and permit the development of design tools.  Models will be extended and enhanced as needed. He will also monitor the field performance of the GCL in the proposed 20 m by 20 m composite liner test site.  In addition to obtaining information about GM wrinkles, this test site will provide data on field hydration of GCLs which influences both its hydraulic conductivity and interface contact conditions with the overlying GM. 

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Badran, Fady

Effect of protection layers on aging of geomembrane liners under chemical exposure, elevated temperatures, and physical stresses

High Density Polyethylene (HDPE) geomembranes are extensively used as component of the primary and secondary landfill liner systems. With time, geomembranes experience aging and degradation during their service life. This research conducts laboratory experiments using steel pressure vessels (0.6 m diameter, 0.5 m high), simulating real life landfill conditions, involving elaborate leachate circulation, temperature, and pressure control systems. The results of the testing program will be used to derive improved estimates of geomembrane service life and to provide options to improve long-term performance of geomembrane liners. In addition accelerated ageing tests will examine the effect of (1) different chemical constituents found in municipal solid waste leachate, (2) geomembrane thickness, on the second and the third stages of HDPE geomembrane ageing.

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Chappel, Melissa

A Field Study of Geomembrane Wrinkles

Geomembranes (GM) are used as barrier in landfill liners and covers, often as a composite barrier system with a geosynthetic clay liner (GCL) to prevent the migration of contaminating fluids. During construction, thermal expansion of the geomembrane may occur as a result of solar radiation, causing wrinkles to develop in the geomembrane.  The magnitude of this thermal expansion, and the resulting size and number of wrinkles is controlled by the thermal properties of the geomembrane as well as the exposure temperature.  The behavior of geomembrane wrinkles in the field is still not fully understood; there are complex factors involved in their development, including material properties of the geomembrane, weather conditions and construction quality control and quality assurance (QA/QC).  The wrinkles will be monitored over two seasons at a field site near Godfrey, Ontario, as well as actual landfill installations across Canada.  The data will be gathered by taking low altitude air photos from a tethered blimp, and the photos will be digitally analyzed to determine the length, area and connectivity of the wrinkles. Laboratory studies will be conducted to look at geomembrane thermal expansion and wrinkling in detail.  Methods of wrinkle reduction will also be tested. (Research is being conducted in association with Drs. R. Brachman and W.A. Take)

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Ewais, Amr

Long-term performance of geomembrane liners

This research investigates the long-term performance of High Density Polyethylene (HDPE) geomembrane (GM). The study includes: (a) aging the GM at different temperature in different exposure media such as air, water and synthetic leachate; and (b) aging of GM as a part of composite liner system at different temperatures. In this study, four GM thicknesses are examined 1.0, 1.5, 2.0 and 2.5 mm to investigate the effect of thickness on the long-term performance of the GM.  Another component of the study involves examination of the the effect of sunlight exposure on geomembrane.

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Goveas, Len

Effect of Dissolved Gas on the Behaviour of Fine-Grained Soils in Excavations near Sarnia, Ontario

Fine-grained soils that become gassy during unloading have been encountered recently and historically in excavations near Sarnia, Ontario. A research program involving laboratory and theoretical modelling is underway to study the behaviour of these soils. The laboratory program involves a custom consolidometer that will allow replication of the in-situ processes by which the soil was deposited, gasified, and unloaded, with photogrammetric data collection to study in depth the volume changes during gas exsolution. A constitutive model suitable for gassy fine grained soils in unloading is being developed, which will be calibrated through the results of the laboratory study, and incorporated into finite element code. (Co-supervised by A. Take)

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Hoor, Azadeh

Thermal behavior of landfill lining system

Heat generated within landfills creates thermal gradients that have the potential to cause outward moisture movement and desiccation of mineral components of composite lining system. Studies are being carried out in order to assess the behaviour of lining system subjected to thermal gradients. Several issues affecting the behaviour of the medium are being explored based on numerical models and experimental studies.

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Lange, Karina

An Examination of GCLs as a potential barrier to the migration of metals leaching from mine tailings and municipal solid waste

The efficiency of GCL’s to attenuate potentially hazardous metals and metalloids that are leached from municipal solid waste and mine waste is being examined. Particular attention is being paid to the containment of As-rich, neutral-pH solutions typical of gold mine leachate. The sensitivity of GCL performance to changes in pH is being examined together with the mechanism of metal attenuation and the adsorption onto bentonite, sorption onto Fe and Mn hydroxides, the effect of reducing conditions on the long-term stability of these hydroxides, and metal precipitation as carbonates, oxides, and sulfates. (Co-supervised with Prof. H. Jamieson).

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Mabrouk, Ahmed

The analysis of a deep excavation in a gassy soil

Develop a finite element model to represent the behavior of gassy soils and to model complex three-dimensional excavations in these soils (with particular reference to two failures that occurred near Sarnia in 1990s which will be used as case histories to verify the predicative capability of the model). This project will involve (a) building a 3D finite element model using Abaqus (b) developing and implementing  a 3 phase gassy soil constitutive model which accounts for the behavior and interaction of the soil particles (solid phase), the pore water (liquid phase) and the methane (gas phase); (c) modeling the transition from the initial conditions two phase conditions (with the gas dissolved in the pore water) to the final three phase conditions; (d) modeling the effect of complex three dimensional unloading conditions on the dissolution of gas and the consequent changes in the soils effective stress and strength response.

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McWatters, Rebecca

Diffusion of Contaminants through Barrier Systems           

Quinn, Pete

The Hazard and Risk to Linear Infrastructure Associated with Landslides in Champlain Clay

The work examines the nature of landslide hazards in sensitive Champlain clay in eastern Canada and their relationship to linear infrastructure.  The study involves: extensive desktop study to develop an understanding of the spatial and temporal distribution of landsides and their potential relationship with physiographic and geological features; in-depth study of the mechanics of large landslides in sensitive clay to understand the geometric, stratigraphic and dynamic conditioning and triggering factors; development of a digital inventory (in GIS) of large landslides in sensitive clay; statistical comparison of landslide locations with digital terrain data to develop a landslide susceptibility model at the regional scale; and, an holistic interpretation of the preceding components to develop a preliminary appreciation of landslide risk to vulnerable linear infrastructure.  The work will support government and industry demands for more effective landslide risk management approaches. (Co-supervised with Dr. J. Hutchinson and Dr. M. Diederichs).

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Taechakumthorn, Chalermpol

The Study of Embankment and Reinforced Wall Behaviour on Rate-Sensitive Clay Foundation Using Finite Element Analysis

Apply the time-dependent elastic-viscoplastic constitutive model using state-dependent viscosity parameters to study the behaviour of embankment and reinforced walls on rate-sensitive clay foundations using Finite Element Analysis. The constitutive model is coupled with Biot consolidation theory formulated using the theory of overstress viscoplasticity, an elliptical cap yield surface, the Drucker-Prager failure envelop and critical state soil concept. The use of techniques such as reinforcement, prefabricated vertical drains and stage construction technique are being examined separately and in combination.

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Yu, Yan

Modeling Leachate Characteristics and Clogging

Based on both theoretical considerations and the findings from both the field and laboratory studies, a model of clogging incorporating combined biological, chemical and physical processes “Bioclog” has been developed to predict the leachate characteristics and clogging properties for the column tests, mesocosm tests under the controlled laboratory conditions, and to model the field collection systems with sand drainage layers. However more work is needed to calibrate the model against measured mesocosm data and develop it, so it is amenable to model field cases with gravel drainage layers and filter-separator layers. The research being undertaking include: (1) adding the capacity to model sedimentation during transport and examining the effects of bacterial sedimentation on the distribution of species concentration and porosity in the leachate collection systems; (2) incorporating a granular filter layer, geotextile filter layer or a combined filter layer in the Bioclog model, and analyze their effect on the service life of leachate collection system; (3) improving the ability to model situations where there is a very wide (many orders of magnitude) variation in hydraulic conductivity of the drainage layer (from very low in the lower portions that are significantly clogged to very high just below the unsaturated zones when the leachate mound rises); (4) using the model to predict field behavior and provide design guidelines.

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M.Sc. STUDENTS

Beddoe, Ryley

Establishment of water retention characteristics of Geosynthetic Clay Liners and subsoil. 

This work will examine and quantify the monotonic wetting and drying, and cyclic wetting and drying behaviour of geosynthetic clay liners (GCLs).  Previous work has not yet been able to obtain the full water retention curve due to the enormous range of suctions needed and the difficulty that presents during experimentation.  Therefore, for this research a new dual-technique device will be implemented in order to obtain the full water retention curve.   This research will also quantify the magnitude of hydraulic hysterisis and cycling of GLC’s.  This will provide industry with an improved understanding of why GCL panels might separate in the field. (Co-supervised by Dr. A Take).  

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Bostwick, Laura

Moisture Uptake and Shrinkage of Geosynthetic Clay Liners
           
The overall aim of this project is to better understand the behaviour of Geosynthetic Clay Liners (GCLs), with tests being divided into two distinct areas.  The first set of tests, which aim to quantify panel shrinkage, are to be conducted at a specially constructed landfill site located north of Kingston.  In addition to field measurements, laboratory tests will be carried out to determine the influence of several factors (such as temperature, moisture content and panel size) on the amount and rate of panel shrinkage and swell.  The project will also investigate moisture uptake of GCLs.  Perspex cells will be filled with soil at a known void ratio and moisture content; a GCL will be placed on top of the soil and the cell allowed to come to equilibrium.  Sealed cells will be monitored with the aid of Xeritron sensors; a second set of cells will see the periodic removal of the GCL samples for weighing. (Research is being conducted in association with Drs. R. Brachman and A. Take)

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