Groundwater Protection with Geosynthetics Clay Liners: Behaviour under Unsaturated Conditions

Summary

Geosynthetic Clay Liners (GCLs) are engineered systems made of bentonite clay sandwiched between two geotextiles and used in conjunction with high-density polyethylene geomembranes (GM) in order to insulate surface contaminants and protect groundwater from contamination. The goal of the project is to conduct a series of experimental, theoretical and computational investigations to develop an accurate characterisation of key hydro-mechanical properties of GCLs, under partially-saturated conditions, and their dependence on temperature, overburden load, type of bentonite, geosynthetics properties as well as manufacturing process.

Please contact the supervisor directly at the following email address for any enquiry regarding this opportunity: abbas.elzein@sydney.edu.au

Supervisor(s)

Professor Abbas El-Zein

Research Location

Civil Engineering

Program Type

PHD

Synopsis

Geosynthetic Clay Liners (GCLs) are engineered systems made of bentonite clay sandwiched between two geotextiles and used in conjunction with high-density polyethylene geomembranes (GM) in order to insulate surface contaminants and protect groundwater from contamination. The combined GCL/GM liner is usually known as a composite GCL. Composite GCLs are capable of operating under aggressive thermal, hydraulic and chemical conditions such as high-temperature, high-salinity or permafrost conditions. However, their failure would lead to significant and costly damage to the environment.   Their development has evolved mostly empirically and, although they are currently widely used worldwide, many gaps remains in our understanding of their thermo-hydro-mechanical behaviours, as well as their long-term performance.   One of these gaps is the characterisation and prediction of the relationship between water content and water suction under unsaturated conditions. This relationship, known as the soil water characteristic curve (SWCC), is a key constitutive equation required for an accurate description of the hydro-mechanical behaviour of porous material under unsaturated conditions. In the case of GCLs, the sandwich structure of the liner, the expansive nature of bentonite clay and the thermal, mechanical and chemical loads to which the liners are subjected adds significant complexity to the characterisation of the SWCC.   The goal of the project is to conduct a series of experimental, theoretical and computational investigations to develop an accurate characterisation of the SWCC of GCLs and its dependence on temperature, overburden load, bentonite and geosynthetics properties as well as manufacturing process. The project will allow a more accurate prediction of the thermo-hydro-mechanical behaviour of GCLs, the development of GCLs with better water retention properties and less propensity for desiccation, and hence better groundwater protection. The successful applicant will be trained in the theoretical and experimental investigation of coupled thermo-hydro-chemo-mechanical (THCM) analyses of unsaturated soil mechanics. He or she will develop an expertise in the design and performance assessment containment systems for the protection of subsurface ecosystems. Papers are expected to be published in one of more leading journals in the field such as Geotechnique, Geotextiles and Geomembranes and International for Numerical and Analytical Methods in Geomechanics

Additional Information

The School of Civil Engineering at the University of Sydney has a long tradition of cutting-edge research and has been ranked 12th in the world in 2013 by the QS World University Rankings.  

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Keywords

groundwater, geosynthetics, Water Retention Curves, hydraulic conductivity

Opportunity ID

The opportunity ID for this research opportunity is: 1971

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